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‘PUBLISHED BY R. M. VAN ARSDALE, ® 


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MorsE BUILDING. ) 
1891. 








CoPpvRIGHT, 1889, 
By AntHuR T. Woops. 





PREFACE, 





In the preparation of the series of articles for the columns 
of the National Car and Locomotive Builder which 
are here collected in book form, the aim of the author was 
to combine the description of the various forms of com- 
pound locomotives which have been actually used, with so 
much of the theory of the design of compound engines as 
would seem to be directly applicable to locomotive prac- 
tice. 

An effort has been made to present an unprejudiced 
analysis of each type, and to point out such advantages and 
disadvantages as are apparently clearly demonstrable, while 
carefully avoiding matters of individual preference. 

Free use has been made of all available material, and 
the authority for data is in general given in the text. The 
author wishes to specially acknowledge his indebtedness to 
Engineering and to Mr. Anatole Mallet, civil engineer, Paris; 
Mr. A. von Borries, locomotive superintendent of the Han- 
over Railroad; Messrs. Henry and Baudry,of the Paris, 
Lyons & Mediterranean Railway, and Mr. G. Du Bousquet, 
of the Northern Railway of France, for courteously supply- 
ing him with information concerning their designs. 


CHAMPAIGN, Illinois, January, 1891. 


IE %\ 


CONTENTS. 


CHAPTER I. 
THEORY OF DESIGN OF TWO-CYLINDER ENGINES. 


CHAPTHEGIL 
THEORY OF DESIGN OF TWO-CYLINDER ENGINES. 


CHAPTER III. 
DESCRIPTION OF THE WORSDELL-VON BORRIES SYSTEM. 


CHAPTER IV. 
DESCRIPTION OF MALLET TWO-CYLINDER TYPE; SIZE OF CYL- 
INDERS, PORTs, ETC. 


CHAPTER V. 
STARTING POWER OF TWO-CYLINDER ENGINES—THE LINDNER 
TYPE. 


CHAPTER VI. 
EcoNoMy OF TWo-CYLINDER ENGINES. 


CHAPTER VIL. 
STEAM DISTRIBUTION IN THREE CYLINDER ENGINES—DESCRIPTION 
or THREE-CYLINDER ENGINES. 


CHAPTER VIII. 
DISTRIBUTION OF WORK BETWEEN CYLINDERS—STARTING POWER 
AND PERFORMANCE OF THREE-CYLINDER ENGINES. 


CHAPTER IX. 
FOUR-CYLINDER RECEIVER ENGINES. 


CHAPTER X. 
FOuUR-CYLINDER TANDEM ENGINES. 


CHAPTER XI. 
COMPARISON OF TYPES—PISTON SPEED—W EIGHT OF RECIPROCAT- 
ING PARTS—RUSSIAN TESTS. 


CHAPTER XII. 
AMERICAN COMPOUND LOCOMOTIVES. 


7 a3 | 


~ Compounn Locomotives. * 


OL ALL Bey if 

The elementary theory of compound locomotives does 
not of course differ from that of other compound engines, 
whether they are condensing or non-condensing, or for 
stationary or marine purposes; but in applying the prin- 
ciples of compound engines to locomotives, while careful 
attention must be given to each of the many items which 
enter into the problem of designing any well-proportioned 
compound engine, it will be found that some factors, which 
are of comparatively small consequence in marine or sta- 
tionary work, become of importance in the locomotive. 
These differences arise largely from the wide range of 
power required from locomotives, and the practical neces- 
sity of keeping the valve gear and operating mechanism as: 
free from complication as possible. On the other hand, the 
recent introduction of higher pressures and greater piston 
speeds in marine practice has rendered some of the work. 
ing conditions of marine engines and locomotives much 
more nearly alike than they have been heretofore. 

ELEMENTARY INDICATOR CARDSs.—The theory of the com- 
pound engine has been so thoroughly discussed by able writ- 
ers, particularly in text books on the marine engine, that 
any further discussion seems almost superfluous; but as the 
most satisfactory method of designing any steam engine is 
to start with the elementary theoretical indicator card, and 
alter and adjust it here and there as experience and the 
special requirements of the case dictate, we will follow that 


10 COMPOUND LOCOMOTIVES. 


methcd as far as practicable in considering compound loco- 
motives. The type of compound locomotive which most 
nearly resembles the ordinary form of simple engine is the 
two-cylinder receiver engine having the cranks at right 
angles, the high-pressure crank leading. In this form, the 
steam, after expanding in the high-pressure cylinder, is ex. 
hausted into an intermediate receiver from which the low- 
pressure cylinder is supplied. We will first consider the form 
of the elementary theoretical indicator cards from such an 
engine, and for the present will assume that there are no 
clearance spaces, that steam is admitted and exhausted ex- 
actly at the beginning and end of the stroke respectively, 
that the point of cut-off is sharply defined, and that irreg- 
ularity, caused by the angularity of the connecting rods, 
may be neglected. If with these assumptions steam is cut 
off at one-half stroke in each cylinder, the indicator cards 
would have the general form shown in Fig. 1. 

The upper card, a, b, c,d, e, f, a, is from the high-press- 
ure cylinder and the lower card, e, f, g, h, k, e, is from the 
low-pressure cylinder. The cards are shown as they would 
be traced by the pencil of an indicator, which is applied. 
first to one cylinder and then to the other, the same spring 
being used and both cards having the same length. The 
two cards are then fitted together as shown in Fig. 1, so as 
to represent the successive actions of the steam in the two 
cylinders, the cranks being at right angles. Referring to 
the high-pressure card, a b is the admission line and b ¢ the 
expansion line, asin a card from a simpleengine. Atc 
the high-pressure exhaust opens, connecting the high-press- 
ure cylinder with the receiver, and the pressure falls to d. 
The conditions which control this drop in pressure ¢ d will 
be discussed later. As we have assumed a cut-off at one- 
half stroke ineach cylinder, the steam valve of the low- 
pressure cylinder closes just as the high-pressure piston 
reaches the end of the stroke at c. Hence, as the high-press- 
ure piston makes the back stroke, the steam is compressed 


COMPOUND LOCOMOTIVES. Tt 


in the high-pressure cylinder and receiver until one-half the 
back stroke is accomplished at e. Here the low-pressure 
valveopens, admitting steam from the receiver to that 
cylinder, and from eto f there is free communication be- 
tween the exhaust side of the high-pressure cylinder, the 
receiver, and the steam side of the low-pressure cylinder. 
At f the high-pressure exhaust valve and the low-pressure 
steam valve close, and the steam expands in the low-press- 





Kk ATMOS? LINE! 
ZERO LINE OF PRESSURE 


Fig. 1 


ure cylinder to the end of the stroke g, when it is exhausted 
into the atmosphere as froma simple engine. The remain- 
ing lines of the cards do not differ from the corresponding 
lines in cards from simple engines. 

FORMULAS FOR CALCULATING PRESSURES.—For calculat- 
ing the pressures at the various points in the cards we can 
without serious error make use of the ordinary formulas for 
‘*‘moist steam,” or in other words, assume that pressures vary 
inversely as the volumes, the curves of expansion and com- 
pression then being rectangular hyperbolas. On this basis 


12 COMPOUND LOCOMOTIVES. 


mean pressures for such lines as a b care determined by the 
1 + hyp. log. r 
"s 
nized as the ordinary formula for mean pressures, and in 
which p, is the absolute initial pressure, r is the ratio of 
expansion, and pm is the gross mean forward pressure, 
The absolute pressure is the gauge pressure plus the atmos- 
pheric pressure, which is ordinarily taken as 14.7 pounds 
per square inch. Tables of hyperbolic logarithms or of 


1+ hyp. log. r 
: 


formula pm = Pp, (1). This will be recog- 


values of the fraction for various values 


of r are given in almost all books on the steam engine, and 
will therefore be omitted here. Asan example of the ap- 
plication of the above formula, let the gauge pressure at 
the point b in Fig. 1 be 145.3 pounds per square inch, so that 
the absolute pressure will be 160 pounds. As cut-off takes 
place at one-half stroke the ratio of expansion r = 2, and 
therefore the final pressure in the high-pressure cylinder 
will be one-half of 160 = 80 pounds. From the tables pre- 
viously referred to we find that for r = 2, pm = .847 p,, and 
therefore pm = .847 X 160 = 185.5 pounds absolute pressure, 
which is the mean pressure between a and c measured from 
the zero line of pressures. This formula is applicable to 
such lines of the card asa be whena bD is parallel to the 
atmospheric line, as it is practically in engines supplied 
from a boiler and working at slow speeds. For calculating 
the mean pressure between b and ¢, d and e, e and f, or for 
other expansions or compressions in which the part of the 
card considered is wholly curved, or where no line of con- 
stant pressure as a b is included, the formula 


pm =P a (2) is to be used. This formula is de- 


duced from the same theoretical considerations as the one 
given above, and the letters represent similar quantities. 
The former covers the whole stroke from a to c, and the 
latter only the curved part of the card as from btoc. For 


COMPOUND LOCOMOTIVES. 18 


example, the pressure at b is 160 pounds and the volume at 
c is twice that at b. The ratio of expansion is therefore 2, 
and by reference to a table of hyperbolic logarithms we find 
pm = 160 — = 160 x .693 = 110.9 pounds between b and 
c. This is for one-half of the stroke, and for the first half, 
from a to b, the mean pressure is 160 pounds, therefore the 
160 = 185.5, 
which is the same as calculated by the first formula. 

To avoid needless repetition, the following symbols, which 
will hereafter be used, are here inserted: 

v = volume of high pressure (h. p.) cylinder in cubic 
inches, 

V = volume of low pressure (Il. p.) cylinder in cubic 
inches, 

C = volume of receiver in cubic inches. 

R = ratio of the two cylinders. 

PRESSURE IN THE RECEIVER.—As before stated, there is 
in the case illustrated by Fig. 1, compression in the h. p. 
cylinder and receiver from d to e, and expansion in the h. p. 
cylinder, the receiver and thel. p. cylinder from e to f. How 
much the pressure varies between d, e and f depends upon 
the capacity of the receiver as compared with the h. p. and 
l. p. cylinders. In the present case, assume the capacity of 
the receiver to be equal to that of the h. p. cylinder, or C = 
v, and let the pressure at e be taken at 96 ponnds. At d the 
steam fills the h. p. cylinder + receiver, and at e it fills one- 
half the h. p. cylinder + receiver ; therefore the compres- 
sion isfromv+ OC = 2vto.5v+ C=1.5 v, and the ratio of 
compression is 2 v + 1.5 v = 1.83. The pressure at dis then 
96 x .75 = 72 pounds, and by formula (2) the mean pressure 
between e and d is 96 x .86 = 82.6 pounds. At /f the vol- 
ume occupied is that of one-half the 1. p. cylinder + receiv- 
er. Assuming for the present case that the I. p. cylinder is 
2.5 times the h. p. cylinder, or R = 2.5, the expansion will 





average for the whole stroke would be 


14 COMPOUND LOCOMOTIVES. 


2.5 V 
2 

sion is 2.25v+1.5v=1.5. The pressure at fis then 96 x 
.67 = 64 pounds, and by formula (2) the mean pressure be- 
tween e and fis 96 X .81 = 77.8 pounds. The following 
table shows the pressures at the points d, e and f of the h. p. 
indicator card with receivers having capacities of v, 1.5 v 
and 2 v, and with cylinder ratios of 2 and 2.5, which give 
a sufficiently wide range to cover present practice in com- 
pound locomotives: 





be from 1.5 v to +- C = 2.25 v, or the ratio of expan- 





l 

















as) S é S “a 
4 3S 3 ae 3 o> 
© os o Os © oo 
ey * ff O 
5 as | ai = a= 
a a3 mn As a r=] 
3) ao a Ry nN e 
2 OQ 2 oe 2 oe 
py = Ay = Ay = 
C= v,R=2..... 80 91.8 | 1067] 91.8 80 91.8 
C=15v, R=2..... 80. 88.9 | 100 88.9 80 88.9 
C=2 v,R=2..... 80. 87.4 87.4 80 87.4 | 
C= v,R=2.5 72. 82.6 96 77.8 64 80.2 — 
C=2 v,R=2.5 69.3 | 75.7 83.2 | 72.4 64 : 


An examiration of this table shows that, with the as- 
sumed cut-offs and relative volumes, the actual pressure in) 


the receiver during one stroke may vary as much as 26.7— 


pounds, and that in all of the cases given the pressure at f, 
or the point of 1. p. cut-off, is considerably below that at e, 
while the mean pressure between e and/f does not differ 
much from the mean pressure in the receiver. In design- 
ing compound engines the pressure in the receiver is 
frequently assumed as constant. 

It will be seen from the above that this assumption does 
not introduce any serious error as far asthe h. p. back 
pressure and the 1. p. mean pressure up to the point of cut- 
off are concerned. But as the pressure at f is considerably 
below the mean receiver pressure, the mean pressure be. 


‘1 
all 


ye 


COMPOUND LOCOMOTIVES. 15 


tween f and g, calculated on the basis of a constant receiver 
pressure, will be too high. In many cases, however, it is 
well-nigh impossible to predetermine the receiver pressure 
by calculations, and the best that can be done is to estimate 
it from the known pressure found in similar engines in 
practice. The nature of these difficulties will appear later, 
and for the present we will continue to calculate pressures, 
assuming as before that there is no condensation in the re- 
ceiver. The table also shows clearly one result of chang- 
ing the relative capacity of the receiver, viz., that the 
larger the receiver thesmaller are the variations in pressure 
in it during a stroke. 

FINAL PRESSURE; TOTAL EXPANSION.—In a compound en- 
gine, a certain fraction of the h.p. cylinder is filled with steam 
from the boiler at each stroke, and after expanding in both 
cylinders this mass of steam finally fills the 1. p. cylinder be- 
fore it is exhausted into the atmosphere or condenser. 
For example, if the cylinder ratio is 2.5 and the h. p. cut- 
off is at one-half stroke, .5 v is the volume admitted from 
the boiler at each stroke, and this finally fills the volume 
2.5 v before it is exhausted. The steam is therefore ex- 
panded to five times its initial volume, or the ratio of total 
expansion is 5, and the final pressure at which it is ex- 
hausted will be one-fifth of the initial pressure, or 32 
pounds in the case we have used for purposes of iJlus- 
tration. Similarly, if the h. p. cut-off was at three- 
eighths stroke the ratio of total expansion would be 
2.5 X § = 22 = 62, and the final pressure in the I. p. cylin- 
der would be three-twentieths of 160 = 24 pounds. It 
will be noted that the only data required in determining 
the total expansion and final pressure are the ratio of the 
cylinders and the h. p. cut-off, or, in other words, these 
results are independent of the capacity of the receiver and 
of the l. p. cut-off. The effect of the size of the receiver is 
seen in the shape of the indicator cards due to the compres- 
sions and expansions ; but how many or how large these 


16 - COMPOUND LOCOMOTIVES. 


variations are does not affect the final pressure. The office 
of the 1. p. cut-off is to control the division of the work be- 
tween the two cylinders. In acompound engine, which 
exhausts into the atmosphere, the steam can be expanded 
economically until the boiler pressure is reduced to the at- 
mospheric pressure. Steam at 160 pounds absolute could, 


therefore, be expanded 77; = 11 times, nearly, if it were 


160 
14.7 
not for losses of pressure by wire-drawing, condensation, 
etc. In two-cylinder compound locomotives, large ratios 
of expansion are practically unattainable on account of the 
large 1. p. cylinders necessary. 

DROP IN PRESSURE IN RECEIVER.—We are now prepared 
to show how the receiver pressures which have been as- 
sumed can be calculated. Taking as before, R = 2.5, C = 
v, h. p. cut-off at one-half stroke, and I. p. cut-off at one- 
half stroke, we have the final pressure at the end of the ex- 
pansion in the 1, p. cylinder equal to one-fifth of 160, or 32 
pounds. The ratio of expansion in the 1. p. cylinder is 2, 
therefore the pressure at the point f is 32 x 2 = 64 pounds. 
Then, knowing the ratio of expansion from e to f, as al- 
ready calculated to be 1.5, we have the pressure at 
e = 64 x 1.5 = 96 pounds, which was assumed for the 
time in calculating the variations of pressure in the re- 
ceiver. Working back from this still further, we find the 
pressure at d as before, 72 pounds, and as the pressure at c 
is 80 pounds, there has been a drop in pressure of 8 pounds 
when the h. p. exhaust opened. When the I. p. steam valve 
closed at f, the pressure of the steam left in the receiver 
was 64 pounds. Then when the h. p. exhaust opened, the 
steam which filled the h. p. cylinder at a pressure of 80 
pounds mixed with this, and gave a resulting pressure of 
72 pounds. This drop represents an actual loss in the effi- 
ciency of the steam in the engine, since when it occurs the 
steam expands witlout doing useful work. Itcan be readily 
avoided, but in remedying this defect we may introduce 
others which are of moré importance. 


COMPOUND LOCOMOTIVES. x 


To prevent drop, it is only necessary to adjust the cut-off 
of the |. p. cylinder so that the volume of steam drawn by 
it from the receiver equals that of the h. p. cylinder. For 
instance, with the dimensions already given in this para- 
graph, it will be evident that when the l. p. cut-off is at 
ss or two-fifths of the stroke, there will be no drop, be- 
cause two-fifths of the 1. p. cylinder is equal to the whole 
h. p. cylinder in volume, and if we withdraw from the 
receiver at each stroke a volume which is equal to that re- 
ceived from the h. p. cylinder, the pressure in the receiver 
will not be reduced. This can also be readily shown by 
calculating back from the final pressure in the 1. p. cylinder 
as before. Suppose ef to represent two-fifths of the l. p. 
stroke instead of one-half, as shown in the figure, then the 
pressure at f would be 32 x § = 80 pounds, which would 
be the pressure in the receiver when the h. p. exhaust 
opened ; and as this is also the final pressure in the h. p. 
cylinder, there would be no drop. There is, of course, 
always more or less drop due to wire-drawing and friction 
in passages which cannot be prevented, and it must also be 
borne in mind that all of these calculations are based on the 
assumption that pressures vary inversely as the volumes. 

MEAN EFFECTIVE PRESSURE ; EQUIVALENT PRESSURE IN 
‘ONE CYLINDER.—With the data already used the mean for- 
ward pressure in the h. p. cylinder was found to be 185.5 
pounds, The mean receiver pressure, or h. p. back press- 
ure, is 80.2 pounds, and thus the mean effective pressure 
in the h. p. cylinder is 135.5 — 80.2 = 55.3 pounds. For 
the l. p. card, the mean pressure between e and f was 
found to be 77.8 and the pressure at f was 64 pounds. By 
formula (2) the mean pressure between fandg is 64 x .693 
=z 44,4 pounds, The mean forward pressure for the stroke 
77.8 + 44.4 

2 


pressure of 18 pounds, or 3.3 above the atmospheric press- 


is then = 61.1 pounds, and assuming a back 


18 COMPOUND LOCOMOTIVES. 


ure, the 1. p. mean effective pressure will be 61.1 —18 = 
43.1 pounds. 

As the ratio between the cylinder areas is 2.5, assuming 
the stroke to be the same in both cylinders, as it generally 
would be in practice, one pound per square inch on thel. p. 
piston is equivalent to 2.5 pounds per square inch on the h. p. 
piston. We can thus readily find the effective pressurein a 
single cylinder, which is equivalent to the effective press- 
ure in the two cylinders of the compound engine. Ordi- 
narily the mean pressure is thus referred to the 1. p. piston, 
although a reference to the h. p. piston is more convenient 
for some purposes. In the present case, the effective h. p. 


pressure referred to the 1. p. piston is — 22.1. The total 


effective pressure referred to the l. p. piston is then 22.1 + 
43,1 = 65.2 pounds. From this we find that the proportion 
of the total work which is done by each cylinder is, in h. p., 
ae - = = .84, and in I. p. = .66. If the press, _ es are re- 
ferred to the h. p. piston, we have 48,1 x 0.5 + 55.3 = 
107.8 + 55.38 = 163.1 as the equivalent pressure in one 
cylinder of the same size as the h. p. cylinder. A common 
practice has been to make the h. p. cylinder of a compound 
locomotive of the same size as one cylinder of the simple 
engine which it is intended to replace. On this basis the 
theoretical compound engine under discussion would be 
developing the same work as the simple engine when the 
latter was developing a mean effective pressure of one-half 
of 163.1 = 81.6 pounds in each cylinder, 

EFFECT 07 CHANGING THE POINT OF CuT-OFF.—If in Fig. 
1 the h. p. cut-off is made earlier, while the 1. p. cut-off re- 
mains as before at one-half stroke, a series of changes will 
be introduced, which are shown in full lines in Fig, 2, the 
lines of Fig. 1 being repeated in dotted lines. Assuming a 
cut-off at three-eighths stroke, the final pressure in the h. p. 
cylinder is 160 X # = 60 pounds, or at c’ instead of ce. Also, 


COMPOUND LOCOMOTIVES, * 19 


as the total expansion is now 2.5 x § = 2° = 63 instead 
of 5, the final pressure at g is reduced to g’, which repre- 
sents 160 < 38, = 24 pounds. Then, as the ‘h. p. cut-off is 
unchanged, the pressure at fis reduced to f’, or 24 x 2 = 
48 pounds. The steam which fills the h. p. cylinder ata 
pressure of 60 pounds is mixed with an equal volume in the 
receiver at a pressure of 48 pounds, giving a resulting 
pressure at d of 54pounds. Theresults of this change are, 
then, that the forward mean pressure in the h. p. cylinder, 





Fig. 2 


the pressure in the receiver, the initial pressure in the 1. p. 
cylinder, and the mean pressure in that cylinder are all 
less than before. The work done by the]. p. cylinder is 
therefore less, while for the h. p. cylinder we have taken 
from one part of the card and added to another part. The 
total work done by both cylinders is, of course, less than 
before, but the proportion done by the h. p. cylinder is . 
greater, and, in fact, the mean effective pressure in that 
cylinder has been increased. When both cut-offs were at 
the same point considerably more work was being done in 
the 1. p. than in the h. p. cylinder, but by making the h. p. 


20 COMPOUND LOCOMOTIVES. 


cut-off the earlier of the two there is less difference in work 
than before, or, in other words, the work may be equal- 
ized by this means. A similar effect will, of course, be pro- 
duced by making the 1. p. cut-off later than that of the h. p., 
and conversely by making the l. p. cut-off earlier than 
that of the h. p. the proportion of the total work which is 
done by the 1. p. cylinder will be increased. The following 
table calculated for R = 2and C = 1.5 v will illustrate 
this: 











Cut-off.| Mean | Mean | Mean h. p. |Total mean in|Propor'’n 

press. | press. |press. referred; one cyl. of work. 

h.p.|l. p 5) De LoD: to 1. p. h.2pold, op. 
4 | 4 | 46.6 54.0 23.3 77.8 a Be ary f 
4 ae, Os 39.6 25.7 65 4 431 38 

es psa ie 48.9 19,6 68.4 soo | etd 

4 | $1] 81.5 60.3 15.7 76.0 .21| .79 





In practice the pressure in the receiver may be less than 
that calculated, on account of losses in the h. p. cylinder 
and passages. The effect of a lower receiver pressure is to 
increase the proportion of work done in the h. p. cylinder, 
so that by adjusting the valve gear to give an.earlier cut-off 
in the h. p. cylinder than in the 1. p., the total work may 
be very nearly equally divided between the two cylinders. 

In Figs. 1 and 2 thel. p. cut-off has been taken at one- 
half stroke, and it was assumed that release occurred in the 
h. p. cylinder exactly at the end of the stroke. If now we 
make the |. p. cut-off later than one-half stroke, leaving 
everything else unchanged, there will he an exhaust from 
the h. p. cylinder, while the 1. p. steam valve is still open, 
which will increase the pressure in the receiver and cause 
what may be called a re-admission in th~ 1. p. cylinder. 
This is illustrated by Fig. 8,in which the h. p. exhaust oc- 
curs at b, causing a rise in pressure to c, from which there 
is expansion as before in the h. p. cylinder, the receiver 


COMPOUND LOCOMOTIVES. 21 


and the 1. p. cylinder until the 1. p. steam valve closes at d. 
A similar effect will be produced by pre-release in the h. p. 


cylinder. An examination of a diagram such as Fig. 4 
a 








0 





Fig. 3 
may make this subject more clear. In this Fig. bc repre- 
sents the stroke of the pistons and the circle the path of the 
crank pins. Taking the direction of revolution as indicated 
by the arrow, when the h. p. piston is at the end of a 
stroke or its crank is at ac, thel. p. crank will beat ac’, 
and the exhaust from the h. p. cylinder which takes place 
at this position of the cranks will cause the rise in the 1. p. 
card shown atc, Fig. 3. Ifthe h. p. exhaust occurs before 
eo 





the end of the stroke, for example when the piston is at d, 
the 1, p. crank will be at a e’, and the 1. p. piston at g, caus- 
ing a rise in the 1. p. card as shown at k, Fig. 3. In cards 
taken from an engine this increase in pressure will of 
course be more gradual, and at high speeds may simply 
cause the 1. p. admission line to be more nearly parallel 
with the atmospheric line, 


ORAL. 





RATIO OF CYLINDERS.—In treatises on compound engines 
formulas are generally deduced for determining the ratio 
between the volumes of the two cylinders, so that the total 
work done by the engine will be equally divided between 
them. As usually given for receiver engines, these for- 
mulas are based either on the assumption that there is no 
drop in pressure in the receiver, or else it is assumed that 
the receiver pressure is constant. The rule most commonly 
given is that R equals the square root of the total number 
of expansions. In designing compound locomotives any 
such rule could be used only for a rough approximation at 
best, and in general would be of no value, since the require- 
ments of construction place a maximum limit upon the 
size of the 1. p. cylinder, which is less than that theoretic- 
ally advisable. 

The ratios which have been used for two-cylinder com- 
pound locomotives range from 2.74 for small engines to 
1.77 for large engines. Mr. Mallet has stated that the 
ratio should not be less than two. Mr. von Borries, in his 
pamphlet on compound locomotives, recommends ratios of 
from 2 to 2.05 for large locomotives with tenders, and 
from 2.15 to 2.2 for tank locomotives. 

These ratios have apparently been adopted by other de- 
signers, as we find that for the greater number of locomo- 
tives, of which records are published, the ratios lie be- 
tween 2 and 2.1. With such ratios the division of the 
work between the cylinders is regulated by adjustments of 
the valve gear. Larger. ratios than these are used for 
small two-cylinder locomotives, but it does not appear that 
ratios smaller than 1.9 have been used except in converted 
inside cylinder engines. 


COMPOUND LOCOMOTIVES. 23 


CLEARANCE.—In discussing the distribution and action of 
steam in a cylinder, the term clearance space, or simply 
clearance, is understood to mean the volume included be- 
tween the piston when at the end of a stroke and the valve 
face at that end, and thus includes the steam port, the 
space between the piston and the cylinder-head, and any 
other spaces which are in communication with the forego- 
ing, such as indicator pipes and cylinder drains. One of the 
principal effects of clearance is to make the effective cut-off 
later than it would be without clearance, and this produces 
results which can be best illustrated by reference to a figure. 
Referring to Fig. 5, let ed represent the stroke of a piston, 
and assume a cut-off at one-half stroke and 10 per cent. 
clearance. Then a b is one-half of e d, and the apparent 
ratio of expansion is two. Lay off e f equal to one-tenth of 
ed,then f e or ag represents the clearance. The volume 
which is filled with steam when cut-off takes place is g b, and 
this expands until it fills the volume of f d. The actual ratio 
of expansion is therefore fd divided by g }, or in the present 

pe ose aa ea 


OS ee eee aaa 1.83 instead of 2. Expressing this 
+k 


as a formula, the actual ratio of expansion = —, in 


which kis the clearance expressed as a decimal of the 
volume displaced by the piston in one stroke, and n is the 
apparent cut-off, or one divided by the apparent ratio of 
expansion. The point c on the expansion curve is, of 
course, higher with a ratio of expansion of 1.83 than with 
a ratio of 2, and hence the mean pressure between 6 and c 
is higher. In making calculations the actual ratio of ex- 
_ pansion should of course be used, but formula (1) will not 
then give correct results,as by it the mean pressure be- 
tween g and c is found, and not that between a and c, and 
acorrection must therefore be made which necessitates ad- 
ditional calculation. It is somewhat better to use formula 
(2), taking the corrected value for 7, and still better in 


24 COMPOUND LOCOMOTIVES. 


most cases to make use of a graphical construction. As an 
example of the application of formula (2), let the apparent 
cut-off be at one-third stroke with eight per cent. clearance, 


Pe ES | 


The actual ratio of expansion is then 33.08 


the mean pressure between b and c will be p, sadl =.594 p,. 


This is for two-thirds of the stroke, and for the first third 
the mean pressure equals p,. The mean for the stroke is 


2 
therefore mes TES bs tl = .738p,. The mean pressure 


calculated by formula (1) without correction would be .70 ‘Dis 






oe AS ee eee ba. | 


ae { ote | oe 






iS 





om — 





oo” 
N 
‘ 
\ 
\ 
> 
' 
' 
' 
' 
4 
4 
: 
! 
' 
t 
© 











Fig. 5 


CONSTRUCTION OF THE EXPANSION CURVE.—A simple 
method of plotting points on the expansion curve is the fol- 
lowing, which requires only a triangle and a straight edge. 
In Fig. 5 let O V be the zero line of pressures, O P the zero 
line of volumes, and p a known point on the hyperbola, 
Through p draw p s parallel to O V, making it of any con- 


\ 


COMPOUND LOCOMOTIVES. 25 


venient length. Draw p k and s ¢t perpendicular to O V 
and draw Os. Through the point u where O s crosses p k, 
draw u q parallel to O V, and where this line cuts s ¢t at q 
isasecond point on the curve. Any number of other 
points can be found from p or q in a similar manner, as in- 
dicated in Fig. 5. An advantage of this method is that the 
distance of a point from O P can be selected at pleasure, as 
it will be always directly under the point to which the 
diagonal is drawn, as q and s, or « and w. 

COMPRESSION.—In considering compression or cushion 
in compound locomotives, we find that it is a factor of the 
steam distribution which it is more difficult to dispose of 
satisfactorily than in simple engines. For economy of 
steam, the pressure in the clearance space when the steam 
valve opens should be equal to the initial pressure, while 
the necessary pressure for cushioning the reciprocating 
parts is a problem in itself. 

There is, of course, no advantage in compressing to a 
pressure higher than the initial pressure. In a simple 
engine having an initial pressure of 175 pounds absolute, 
and a back pressure of 18 pounds absolute, it is possible to 
compress to 9.7 times the back pressure before the initial 
pressure will be exceeded. If the same pressures are taken 
in acompound engine, for the h. p. initial pressure and 
the 1. p. back pressure, we have the same possible range of 
compression, but it is divided between two cylinders. If 
the receiver pressure is 70 pounds absolute, the possible 
range of compression is for the h. p. cylinder from 70 to 
175 pounds, and for the 1. p. cylinder from 18 to 70 pounds, 
or 2.5 times in the former and about 3.9 times in the latter. 
It will be at once apparent that the valve adjustment for 
compression in the compound is a much more difficult 
problem than in the simple engine. For example, with 
5 per cent, clearance, and the pressures as just stated, 
the pressure in the clearance space at the end of 
the stroke would equal the initial pressure in the h. p. 


26 COMPOUND LOCOMOTIVES. 


cylinder when the exhaust closed at 2.5 x .05 — .05 = .075 
of the stroke from the end, or at 92.5 per cent. of the 
stroke, as it is frequently stated. In thel. p. cylinder, an 
exhaust closure at 85.5 per cent. would fill the clearance 
space with steam at receiver pressure. With 10 per cent. 
clearance, and the same pressures as before, the earliest 
allowable points of exhaust closure would be 85 per cent, in 
the h. p. and 71 per cent. in thel. p. cylinder. It will be 
seen from this that a large percentage of clearance in a 
compound engine may be a positive advantage. The rela- 
tions between the back pressure, the pressure from com- 
pression, the point of exhaust closure and the clearance, 
can be expressed in a general formula as follows: Refer- 
ring to Fig. 5, let p’ represent the back pressure and p” the 
pressure in the clearance space at the end of the compres- 
sion, both measured from the zero line of pressures; let J 
be the point of exhaust closure, 1 m the compress n curve 
which is considered asa rectangular hyperbola, d e the 
stroke of the piston, and fe equal k, the clearance as be- 
fore. Then the fraction of the stroke at which the ex- 
haust should close to produce a pressure p” is 
d 1 +? 
tai et —1 Jb. (3) 

The problem of determining the amount of compression 
necessary to cushion the reciprocating parts does not differ 
essentially in compound and simple engines, and for that 
reason will not be discussed at length at this time. The 
work done in compressing the steam from / to e, Fig. 5, ex- 
ceeds that done by the steam on the other side of the pis- 
ton during the same time, and this excessof work tends to 
retard the piston. It will be evident that in determining 
the amount of this excess we can regard the back pressure 
line as the zero line of pressures, if it is parallel to the at- 
mospheric line, and then determine how much the area 
1m e exceeds the area of an equal length from the other end 
of the card. The actual pressure of the back pressure line, 





COMPOUND LOCOMOTIVES. 27 


or whatever line is used for a zero line from which to 
measure pressures, is therefore of no importance in this 
connection, and hence the problem will be very similar in 
all steam cylinders. 

INDICATOR CARDS IN PRACTICE.—The indicator cards 
taken from compound locomotives in practice will, of course, 
differ greatly from those which have been called elementary 
theoretical cards, and which were illustrated by Figs. 1, 2 
and 38. The cards taken from the engine should agree very 
closely with theoretical cards which are drawn according 
to a complete and correct theory. What has been called 
the elementary theory is not strictly correct, andis incom- 
plete ; but it is preferable for practical purposes to a more 
accurate construction on account of its simplicity, and be- 
cause we cannot predict the exact form of an indicator 
card from an engine, which differs from existing types to 
an appreciable extent. 

The causes which produce modifications of the elementary 
theoretical card, are chiefly the initial condensation and 
re-evaporation during expansion; the size, shape and loca- 
tion of the steam passages and the receiver; pre-release and 
compression ; wire-drawing due to gradual opening and 
closing of ports, and the effects of high piston speed. 

Indicator cards from a compound locomotive, in which 
steam was cut off at about four-tenths of the stroke in both 
cylinders, are shown in full lines in Fig. 6. The clearance 
space is 10 per cent. of the piston displacement in the h. p. 
cylinder, and 7.5 per cent. in thel. p. cylinder. The vol- 
ume of the receiver is one and one-half times the h. p. 
cylinder. With this data the theoretical lines shown dotted 
in the figure have been constructed, making allowance for 
the excessive drop shown between the two cards. The 
differences between the actual admission and expansion lines 
of the h. p. card are the same as in cards from simple 
engines, and are due to the wire-drawing during admission 
and at cut-off, and to the re-evaporation during expansion. 


’ 


28 COMPOUND LOCOMOTIVES. 


The extent of these departures from the assumed theoretical 
curve varies greatly in simple engines, and probably depends 
upon the piston speed, together with apparently small 
differences in valve gear and steam passages. The only 
satisfactory way of determining the probable loss in a pro- 
posed engine, whether simple or compound, is to examine 





Sot aah 


o- 


Be oceocme es = woe mmm em eer eee Ss SH RH PR SH Se Se Sew owe ora 


Fig. 6 


indicator cards from an existing engine of the same general 
proportions, and having a valve gear of the same type and 
dimensions. This is also true of the loss of pressure be- 
tween the boiler and the cylinder. Indicator cards taken 
from engines of various makes when on similar service 
show variations in these particulars of as much as 20 per 
cent., and it is obvious that no general rule can be laid 
down. 


COMPOUND LOCOMOTIVES. 29 


In Fig. 6, when the h. p. exhaust occurs at }, the 1. p. 
piston is at m, and re-admission to the 1. p. cylinder takes 
place, causing a rise in pressure to m. The l. p. piston 
moves from this position to that of cut-off f, four-tenths of 
the stroke, before the h. p. piston has moved over the re- 


—170 








H. P. Cut-off. 70% 
LP” ” 84.5% 
Rev. p.min,. 42 














H, P, Cut-off. 50% 
Depa Be 
Rey. p. min. 147 








Fig. 7 


mainder of its stroke from b toc, The pressure at c was 
calculated approximately on the basis of the receiver 
pressure when the h. p. exhaust opened, being that at f; 
but if the valve opened with sufficient rapidity this point 
would be found directly below b. From c to d there is 
compression as shown, and from d there is expansion until 


30 COMPOUND LOCOMOTIVES. 


compression in the h. p. cylinder begins; but with the 
proportions above given, this expansion line is nearly 
parallel to the atmospheric line, or in other words, there is 
practically no expansion. Turning now to the l. p. card, 
and taking the pressure at e as that of the steam in the re- 


—140 





H. P, Cut-off. 30% 
LP.” ” 40% 
Rev. p. min. 150 













— 145 


Rev. p. min. 180 





Fig. 8 


ceiver, we find that the line from e ton is practically at 
constant pressure, and that the rise in pressure from n to m 
is comparatively slight. Also, that during the expansion 
from m to f the fall in pressure is not great. The drop be- 
tween the h, p. and the 1. p. cards in this figure has been 
referred to as excessive, and data which would furnish an 


COMPOUND LOCOMOTIVES. 31 


explanation are not at hand, but this does not lessen the 
value of the cards for our present purpose. 

In Figs. 7 and 8 are shown indicator cards from two- 
cylinder compound locomotives at different speeds and 
points of cut-off. The shape of the h. p. back-pressure line 
is to be noted. Cards Nos. 2 and 3 are from the same 
engine, and it will be noticed that the compression up to 
about the middle of the back stroke is quite marked, and 
that the remainder of the back-pressure line is nearly 
horizontal, as it was found in Fig. 6. In Nos. 4 and 5 the 
compression appears to continue during the whole of the 
back stroke. This is found to be the case in a considerable 
number of cards which have been examined, and is particu- 
larly noticeable at high speeds. 

It will also be seen that the 1. p. cards do not differ 
much in appearance from cards taken from simple 
engines. This would seem to indicate that we can without 
great error consider the receiver pressure as constant, and 
therefore treat the 1. p. cards as if they were actually taken 
from simple engines. This arises largely from the effects 
of re-admission. It is not likely that, with the ordinary 
valve gear, the h. p. release will occur later than at 90 per 
cent. of the stroke, and an examination of a diagram of 
the crank positions such as Fig. 4, will show that the 1. p. 
piston has moved over 20 per cent. of its stroke at this 
position. 

The |. p. cut-off will not generally be earlier than three- 
tenths of the stroke, and hence it is safe to say that re- 
admission will always occur in practice. We have already 
seen that the practical effect of this is to make the 1. p. ad- 
mission line more nearly parallel with the atmospheric line, 
or, in other words, causes the l. p. admission line to more 
nearly resemble the admission line of a card from a simple 
engine. 

In Fig. 9 are shown the admission and expansion lines of 
four indicator cards from the 1. p. cylinder of a compound 


32 COMPOUND LOCOMOTIVES, 


locomotive. The points of cut-off given are those which 
were recorded on the cards. The dotted lines indicate the 
form of the theoretical card for these points of cut-off and 
for the initial pressures as shown. 








Cut-off. 60 % 
R.p.m. 120 







OSD re am ome ee oe ee ee ee 


Cut-off. 50% 


Cut-off, 40 % 
R.p.m. 180 





Cut-off, 30 % 
R. p.m. 170 


lL SOO 2 PCOS S 222822 22 OSES EH € BEG SSlPF*SVPASCA SVIZFEQSFeCSS er Sat So a oe 


On card No. 6 a curve which agrees with the actual 
curve very closely is indicated by dots, and shows an earlier 
cut-off than that recorded. On card No. 9 the irregular 
dotted line shows the form of the card from the other end 


COMPOUND LOCOMOTIVES. 33 


of the cylinder with the same nominal point of cut-off. It 
will be apparent from Fig. 9 that the 1. p. cards do not 
differ more from the elementary theoretical cards for 
simple engines than do the actual cards taken from these 
engines, 

To obtain a fair idea of the probable form of the cards 
from a compound locomotive but one factor now remains 
to be determined, and that is the probable pressure in the 
receiver. On this hinges the division of work between the 
cylinders, and there is, in fact, no general rule by which it 
can be calculated with any certainty. The size of steam 
passages, and the size and location of the receiver, all steam 
space between the valves of the two cylinders being in- 
cluded in this term, will control this pressure to a great ex- 
tent, as upon these depend the losses of pressure due to 
friction in passages and to condensation. Mr. von Borries 
states, in his pamphlet on Compound Locomotives, that 
for cut-offs of from 30 to 40 per cent. the pressure in the 
receiver should be from 30 to 33 per cent. of that in the 
boiler. If the pressure maintained in the receiver of an 
engine in practice is known, the probable receiver pressure 
in asimilar proposed engine can of course be predicted 
with some degree of certainty; but when any different ar- 
rangement of valves and passages is used, the distribution 
in previous engines can serve as a guide only. The follow- 
ing is suggested as a method of approximating to the prob- 
able receiver pressures. With the same initial pressure in 
the h. p. cylinder, as the h. p. cut-off is made later the 
receiver pressure will become higher, and a similar effect 
is produced by making the 1. p. cut-off earlier. Hence a 
formula for calculating the receiver pressure should have 
the form p =c X p; he wae In this formula p is the 
absolute receiver pressure, p, the absolute h. p. initial pres- 
sure, and c is a numerical coefficient. 

An examination of a considerable number of indicator 


34 COMPOUND LOCOMOTIVES. 


cards from compound locomotives gave an average value 
for c of 0.46, but this value is not recommended except for 
approximations, and of course no such formula can take 
the place of direct experiment. 

COMBINED INDICATOR CARDS.—It is a common practice to 
combine the indicator cards taken from the several cylin- 
ders of compound engines in one diagram, and to compare 


i 






ps) 
ee aes ee re 





Fig. 10 


this with an assumed curve of reference. The expansion of 
the steam in two or more cylinders can thus be compared 
approximately with an equal expansion in one cylinder, 
but itis not clear that much can be learned from such a 
diagram. The reference curve is ordinarily the rectangular 
hyperbola. Fig. 10 illustrates a combined diagram from a 
compound locomotive, of which the separate cards as taken 
closely resembled card No. 4 (Fig. 8). In Fig. 10 vertical 
distances represent pressures, and horizontal distances rep- 


COMPOUND LOCOMOTIVES. 35 


resent volumes as usual, Both cards must first be reduced 
to the same scale of pressures. Then take any convenient 
distance such as bc to represent the volume of the l. p. 
cylinder, and let a b represent the volume of its clearance 
space. Then Oa P isthe zero line from which to measure 
volumes, and O V drawn as usual is the zero line of press- 
ures. Lay off ad equal to the h. p. clearance space, and 
d e equal to the volume of the h. p. cylinder, both on the 
same scale as that of the 1. p. cylinder; or de should equal 
bec divided by theratio of the cylinders. The outlines of 
the cards are then found by plotting points as usual. 


OPA tue eee 





GENERAL ARRANGEMENT OF PaRTSs.—While the disposi- 
tion of cylinders and steam chests with regard to the boiler 
and running gear in two-cylinder compound locomotives 
does not differ from European practice in simple locomo- 
tives, the same diversity of design, which has heretofore 
been remarkable in that as compared with American prac- 
tice, is found in their compound locomotives. The designer 
will thus find precedent in existing engines for almost any 
arrangement of the principal parts, and for any type of 
valve gear which he is likely to adopt. 

The credit of having inaugurated the present era of com- 
pound locomotives in Europe is due to Mr. Anatole Mallet, 
who designed successful two-cylinder compound locomo- 
tives for the Bayonne & Biarritz Railroad in 1876, and 
has since brought out many different designs. While it 
would not be incorrect to class the greater number of 
compound locomotives as belonging to the Mallet system, 
this term as applied to two-cylinder engines is usually re- 
stricted to those which can be operated either as simple or 
compound engines at the will of the engineer, as distin- 
guished from others which are necessarily worked as com- 
pound engines, except for a brief interval in starting. 

Engines of the latter class have been built in consider- 
able numbers since 1880, especially after the designs of Mr. 
A. von Borries, Locomotive Superintendent of the Hanover 
Railroad, and Mr. T. W. Worsdell, Locomotive Superin- 
tendent of the North-Eastern Railway, England. 

This class of engines comprise what is known as the 
Worsdell and von Borries system, the essential difference 
between their designs being in the method of accomplishing 
the automatic change from simple to compound working. 


COMPOUND LOCOMOTIVES. 37 


THE VON BoRRIES SySTEM.—Figs. 11 and 12 illustrate the 
arrangement of cylinders and steam connections in two 
designs of compound locomotives according to the von 
Borries system. In both figures h is the h. p. cylinder, 7 is 
the 1. p. cylinder, A is the steam pipe from the boiler 





to the h. p. cylinder, C is the receiver connecting the 
two cylinders, V is the starting and intercepting valve, B 
is the auxiliary steam pipe from the boiler to the starting 
valve, and D is the exhaust pipe from the 1. p. cylinder. It 
will be noted that in Fig. 12 the steam pipes, receiver and 
exhaust pipe are almost entirely inclosed in the smoke-box, 
and it is very desirable that they should be so placed. 


38 COMPOUND LOCOMOTIVES. 


The arrangement in Fig. 11 is that of asix~<oupled | 
freight engine for the Prussian State Railways, which was 
illustrated in Engineering of Feb. 1, 1889. The dimensions, 





which are of immediate interest in this connection, are as 
follows : 
Diameter of high-pressure cylinder Wiehe ae eat Bek surriee oss on ae Bek eae 


JOW-PLOBSULO tae ite ate eat notes cee soledels 25.6 ** 
Stroke; of DiShOMs.)./0 tas welse. age canciones Matos Peed ote atellacter ener oa akman 
Diameter of driving wheels.............. AC ROM e ayeen bey SaenthOov au 
Boiler pressure, gauge........... Jose aesneucstecseuses veeeeenne 174. Ibs. 
Diameter of boiler, smallest inside........... iv ade emiecs ween 50.8 in. 
Tubes, 184, 2-in. |: lengths. svcd tees ar tune eee coh aes ie 14 ft. 7 in. 
Grate QPGRs 64) ic 6 1.4 40 SINS aid Salde ca wtu ta deinen wey nied 16 sq. ft. 
Heating BOYACE) Cocina kh os coset abies 0 ta ie oicletate @ carom l aot ties 
Weight in working order, all on driving wheels.........-. 88,250 lbs. 
Valveieearin scion sane natives oe AAG Friar ete nil ata quae esate bites Allan. 


Fig. 12 is taken from a paper on Compound Locomotives 


COMPOUND LOCOMOTIVES. 39 


by Mr. R. Eerbert Lapage, read in November, 1888, before 
the Institution of Mechanical Engineers (England), and il- 
lustrates a four-coupled passenger locomotive of the Santa 
Fé & Cordoba Great Southern Railway. The principal 
dimensions are as follows : 


Diameter of high-pressure cylinder. Dee ier ca bata & hae ways aletahs 16 in. 
LOW-E OSSTIPe went Ue temic a o's ce ee case creeae i 
erm SR COIN. oi 6255 clic cas ha aen socidies saddens cannes bicep es Pd DS: 
Veet Ot CLEAVING WCOIB 65 onc oy ccc ince scececcerecceccsasyes 66" ‘¢ 
Boiler pressure, ZAUGC.........cecceeeccerecesenecercees iiseisierd 170 lbs. 
OO MreG AU VROLMIN OS OTOCR. cccccs csr whcwndeccaveccescdas ses 86,200 ‘ 
ee re grea dia uy vice ed ¢aabkdok sts Gack ae Cawases Stephenson. 















er LA 





fees ee MLS 
(im LA 


Fig. 13 


The essential feature of the von Borries system is the 
combined intercepting and starting valve, a recent form of 
which is illustrated by Fig. 13. In this figure a is the re- 
ceiver pipe which leads from the h. p. cylinder and Db is 
the passage to the 1. p. cylinder. The valve is shown in 
the position which it occupies ordinarily, or when the loco- 
motive is working as a compound engine, the direction of 
the flow of the steam being as indicated by the arrows. 
Connected to the back of the intercepting valve v are two 
small plungers ¢ c which together form the starting 
valve. Supposing the valves to be in the positions shown 
in Fig. 13 and the engine about to start, when the throttle 


40 COMPOUND LOCOMOTIVES. 


is opened steam will be admitted to the h. p. cylinder by 
the usual pipe, and also to the auxiliary steam piped, and 
by the passage shown, to the back of the plungers. The 
pressure on the ends of the plungers is sufficient to move 
the intercepting valve v to the left in the figure until it 
seats ate. By the same movement two small ports hh 
are uncovered, through which steam from the boiler is ad- 
mitted to the passage b and thence direct to the 1. p. steam 
chest, while, as the intercepting valve is closed, this 
pressure does not act against the h. p. piston. 

As the engine starts and the exhaust from the h. p. 
cylinder takes place, the pressure in the receiver rises until 
it is sufficient to overcome the pressure on the I. p. side of 
the intercepting valve, when this valve is moved back to 
the position shown in the figure, while at the same time 
the two small steam ports are closed by the plungers, and 
the engine begins to work asa compound, It is said that 
in practice the pressure of the steam from the boiler which 
is admitted to the 1. p. cylinder is reduced by wire-drawing, 
due tothe small steam pipe and ports, to about one-half the 
boiler pressure, and as the ratio of the cylinders is about 
two, the total pressure on the two pistons in starting is 
nearly equal. To prevent excessive pressure in the l. p. 
cylinder and receiver a safety valve is placed on the latter. 

The pressure in the receiver when running is sufficient to 
overcome the boiler pressure acting on the ends of the two 
small plungers, together with the atmospheric pressure on 
the stem of the large valve v, and, therefore, the valves are 
maintained in the position shown in Fig. 13 as long as the 
throttle is kept open. In the paper referred to above, Mr. 
Lapage states that: ‘‘In practice it takes only from half to 
one revolution before the exhaust from the high-pressure 
cylinder opens the intercepting valve and closes the start- 
ing valves.” 

It will be noted that according to this statement, an 
engine with 66-inch driving wheels would begin to work as 


COMPOUND LOCOMOTIVES. 41 


acompound after moving through from about 84 to 17 
feet. Just how far it will move before opening the inter- 
cepting valve will depend upon the positions of the cranks 


\ 
\ 
i} 

\ 
1 
! 
| 
' 
U 





before starting, as will be demonstrated when considering 
the subject of the starting power. Strictly speaking, these 
locomotives can never work as simple engines, since the 
h. p. cylinder always exhausts into a closed receiver and 
never directly into the atmosphere. Mr. Lapage also stated 


42 COMPOUND LOCOMOTIVES. 


that this automatic starting and intercepting valve had 
been already applied to about one hundred and fifty 
engines. 

The earlier forms of intercepting valves were not wholly 
automatic in their action, but required to be closed by 
hand before opening the throttle in starting. In this 
form there were no small plungers, and the steam was 
admitted around the valve stem k, which was fluted for 
part of its length for this purpose. The valve was also 
connected by a bell-crank arrangement to a weighted arm, 
which held the valve open and prevented rattling when 
running with steam shut off. 

THE WORSDELL SysTEM.—Fig. 14 illustrates the arrange- 
ment of the cylinders and steam connections of a Worsdell 
four-coupled compound locomotive for passenger service, 
drawings for which were published in Engineering of 
March 30, 1888. More recent engines do not differ from 
this in regard to the cylinders and steam connections. In 
Fig. 14, h and7 represent the high and low-pressure cyl- 
inders, respectively, A is the high-pressure steam pipe, Cis 
the receiver, Dis the low-pressure exhaust pipe, B is the 
steam supply to the starting valve v, and V is the intercept- 
ing valve. 

The principal dimensions of this engine are as follows: 


Diameter of high-pressure cylinder viele si¥s siair pie cies sete nie sieht eae 18 in. 
low-pressure «| “S8° beer, JLo eosin bone eerie 26 7 eee 
Stroke’ of pistonS):: $25.22. s2sset een eee ee ee PwC Recreate Rr ee Ve 
Diameter of driving wheels..................- Tua Eby pen ee 8014 * 
Boiler pressure, Gatiwe.. is. soi Seccee cacesice cd ten eee ane au lbs. 
Diumeter of boiler, smallest inside... <.co.«. so Checscsanene in. 
Tubes, 242, 134 inches, Lene ba. oy fe oe et ae ee 10 feet it, ss 
Grate area..........-... bobaiek usa locates dhe dedey have een Meee sq. ft. 
Heating SUriace < 272.0 ls csel sssscueeukse> seas at este nee bE 38 3 _ 
Weight in'-working order, total... 0. .<.:ses sn cease enue .97,000 lbs. 
‘ cy = es on driving wheels............. 68,000 ‘* 
ValVe SCaty .as<ck voces tvs sigs sch es pwee seeds seatete ene ee Joy. 


The Worsdell starting and intercepting valves are illus- 
trated by Figs, 15 and 16, which are reproduced from Engi- 
neering. The intercepting valve is a flap valve, and is 
shown in Fig. 15 in the position which it occupies when the 


COMPOUND LOCOMOTIVES, 43 


engine is working as a compound, being swung to one side, 
and thus leaving a straight, clear passage by it. The 
spindle on which the valve turns passes out through the 










Z 
VQ 









CUD : 
Gr S 
RZ 
\S 





Wy 








WHY 







2 A 
TA i 






Interbepting 


Valve Chamber. NN 












na a eee eenemcnnenenneees f 7 SM KF 


Sr 
bil 





04 BE Se 
REF CIOL LALLA LULA QL 






SS 









% 
4 
Yj Y 
ESSSSSSSSSS SSS S OSS SSS SSS SS TS NS SS NT SSSA 
SY AS y 


ESSSSSS 









me 
ASR € 
valve. 
“a D as 


eee eam to starting valve 











CS AAAAY 

















SY ESS8 
DV as She 


Foss | aS ' ¢ 
HEAL Hii | Brom 
vay ut i 





‘ 
Intercépting 
Valve pamper. 
















Lido 


Ye 





SS _wQ77~7 aws3s5yq 





Fig. 16. 





side of the smoke-box, and carries an arm, which is con- 
nected to the small piston shown at a, Fig. 16, in a manner 
which is clearly indicated in the figures, The starting valve 
casing is connected to the main steam pipe by a small pipe, 
which is shown in Fig. 16 and also in Fig. 14. The piston 






44 COMPOUND LOCOMOTIVES. 


a, which operates the intercepting valve by means of the 
connection previously referred to, works in a cylinder 
which is an extension of the starting valve casing. 

A small port, which is covered by a spring-loaded valve, 
connects this cylinder with the pipe b, and thus to the inter- 
cepting valve chamber. The starting valve is operated by 
a lever, and is a double valve, a slight movement of the 
lever opening the smaller valve, and further motion open- 
ing the larger valve, which is then partially balanced. 

The operation of these valves in starting is as follows: 
The starting valve being opened by the engineer, steam, at 
boiler pressure, acts upon the small piston a, and moves it 
forward or to the left in the Figs. By the same move- 
ment the intercepting valve is swung up and closed, and 
the port connecting with the pipe b is uncovered, thus ad- 
mitting steam from the boiler to the intercepting valve 
chamber below the valve, and thence to the low-pressure 
steam chest. As the exhaust takes place from the h. p. 
cylinder, the pressure in the receiver, above the intercept- 
ing valve, rises until it is sufficient to open that valve, 
when, by its movement, the small piston ais returned to 
the position shown in Fig. 16, and the steam supply is thus 
shut off. It ‘will be seen that the Worsdell starting and 
intercepting valves are the same in principle as the von 
Borries valves, although the former are not wholly auto- 
matic in their action. 

Valve Gear Adjustments.—In discussing the theory of - 
two-cylinder compound engines, it was shown that the 
division of the total work between the cylinders could be 
equalized by maintaining a considerably earlier cut-off in 
the h. p. than in the 1. p. cylinder. 

Mr. von Borries finds that in practice for cylinder ratios 
of from 2 to 2.05 a cut-off of 0.4 in the h. p. cylinder calls 
for a cut-off of 0.5 in the l.p. cylinder. This adjustment 
gives a very nearly equal division of the work, and can be 
made without difficulty or increased complication with the 


COMPOUND LOCOMOTIVES. 45 


valve gears which are suitable for locomotives, such as the 
Stephenson, Allan, Joy and Walschaert. 

For the American form of the Stephenson shifting link 
motion, and when the locomotive is to run principally in 
forward gear, only a very simple change..is-necessary, It 
is to make the h. p. link hanger slightly, Shorter’ than the 
1, p. hanger, leaving all other parts as fora, simple énging. 
This causes the h. p. link to be Tittle nearer the mid posi- 
tion than the l. p. link for ali points in the forward géar, 
the result being to make the h. p\ cut-off the earliér of 
twoas required. For theabove @ylinder ratios. the h. 
hanger should be about one-twentiéth of/ the lift of the fink Z 
shorter than that of the 1. p. gear. — 

This difference in length, of course, pr oduces the 5 nite 
effect in the backward gear, the 1. p. cut-off being then the 
earlier. For this reason the full-gear notch is the only one 
cut in the quadrant for the backward gear. Mr. von Bor- 
ries gives the following as the approximate cut-offs which 
are obtained by this means: 







Forward. Backward. 
High-pressure cylinder...... = (OO 20" 807° 20 78 
Low-pressure cylinder....... T85 FO0s  GO0E* $41 am 2) SZ 75 


A more detailed tabulation of the distribution effected by 
this form of adjustment, as applied to the locomotive illus- 
trated by Fig. 12, is appended. Thistable is taken from the 
paper by Mr. R. H. Lapage, to which reference has already 
been made. 

For locomotives which are required to run equally well 
in either direction, the alteration described above is evi- 
dently not applicable, but a similar effect is produced by 
making the mid-gear travel of the 1. p. valve less than that 
of the h. p. valve. This is, of course, readily accomplished 
by reducing the angular advance for the l. p. eccentrics, 
‘the outside lap of the 1. p. valve being also made less. 
For cylinder ratios of from 2.15 to 2.2 Mr. von Borries 
recommends making the mid-gear travel of the 1. p. valve 
0.9 of that of the h. p. valve, and reducing the outside lap 






) 


46 COMPOUND LOCOMOTIVES. 


STEAM DISTRIBUTION IN COMPOUND LOCOMOTIVE ON THE SANTA 
FE & CORDOBA GREAT SOUTHERN RAILWAY. 


Angle of eccentrics, forward, 60% degrees; backward, 614% degrees. 
HIGH-PRESSURE CYLINDER. 


Sixteen inches diameter by 24 inches stroke. Clearance in link, 
top, 0.94 inches; bottom, 0.31 inches. Slip of block, top, 0.81 inches; 
bottom, 0.69inches. Mid-gear travel, 2.63 inches. Outside lap, 1.12 
inches; inside clearance, 0.25 inches. Length of ports, 12.87 inches. 
Length of link hanger, 14.06 inches. 














Maximum 
- |Travel F Cut-off, Release 
Notch in Opening { : 
of Lead. Per cent. | Percent. 
Quadrant.|v sive, A of Stroke. | of Stroke. 
Inches. ee bene 139% 80 
Aparna IPS bse) 
| A. 4 
S| ff sallow | ta | Be | ae 
: . A. 4. 
= 4 3.194 | 0:10 0.47 49 634 
E : 3 ors | 10e1d of erste 411% 16 
mt oo) 3h | Be | Be 
S 2 | 272)! 0716 | 0°38 27h 63 
[ 1 9.624| 0-13 0.16 1614 58 
; 0.16 0.22 18 54 
HH be ® 0.12 0.25 2614 6134 
f Seat 2.72) | 0.13 0.22 20 59 
s |emes | 291) or | oos | S* | bare 
| Sas 2 | 3 ogf| 0.09 0.47 47 7514 
Bei Gerce tiee 0.10 0.38 4216 75 
S | S°d | garf| 0.06 0.62 5534 7934 
= Sosos : 0.09 0.51 5314 81 
il 3.624 | 0-08 0.74 6234 8334 
Alen late] fe | wt | ae 
i 4 914 
( | Full | 4.2611 0:00 | 0.95 7446 9014 


in about the same proportion. The approximate relative 
cut-offs thus obtained are as follows, being the same in 
both forward and backward gear : 


High-pressure cylinders... ks. 024 sence ae usck aa eenet 75 60 50 40 30 
Low-pressure cylinder...... Suiliseensceewentcamenuents 78 64 55 45 34 


COMPOUND LOCOMOTIVES. 47 


STEAM DISTRIBUTION IN COMPOUND LOCOMOTIVE ON THE SANTA 
Fr & CORDOBA GREAT SOUTHERN RAILWAY. 


Angle of eccentrics, forward, 60% degrees; backward, 61% degrees. 
LOW-PRESSURE CYLINDER. 


Twenty-three inches diameter, by 24 inches stroke. Clearance in 
link, top, 0.31 inches; bottom, 0.94 inches. Slip of block, top, 0.81 
inches; bottom, 0.62 inches. Mid-gear travel, 2.56 inches. Outside lap, 
1.12 inches; inside lap, 0.00. Length of ports, 17.00 inches. Length of 
link hanger, 14.64 inches. 





Maximum 
_ |Travel ; Cut-off, | Release, 
Notch in of Lead. OPenhis Per cent. | Per cent. 


Quadrant. vive, pies of Stroke. | of Stroke. 


| rr | yf 


Inches.|Inches.| Inches, 
1.16 





ra 78 933/ 

[Fa | ero | ro | ie | 

fH . . 4. 

a 5 8.72)! 9:06 | 0.87 66 8934 
“ 0.09 0.87 5734 8646 
5 = 3.o0f| 0.09 0°84 51 8346 
S 0.10 0.86 4846 8234 
E ‘ Werte Ol 0:72 40 7914 
; Se ieieolams |B, 
4 4. 

( 1 2.784) 0°16 0.66 Ihe 71 
= 0.13 0.55 17 6214 
( 2.62) | 0:16 0.56 13% 6116 

> set tile 0 62 2714 70 
Bo See ay tka. cs 3654 1394 
eecceee eveces . ola 4 4 

i) 2.905} 0:16 0.69 3134 "7 

Babe ses Bosh ta shh fe O00 0:84 47 81 
ip 0.13 0.78 4384 8214 

hol ie ee late oh ig 0-08 0.87 BBG 

FE ; 0:12 0.87 53h4 8614 
See site| te | sh | we 
A 4 A. 4 


Similar variations in the points of cut-off can be obtained 
with the other types of valve gears which have been men- 
tioned, for example, by placing the arms on the lifting 
shaft of the Allan motion at an angle with each other, 


48 COMPOUND LOCOMOTIVES, 


and by inclining the sliding links of the Jey gear. Other 
minor changes which will produce similar results will 
naturally occur to the designer, 

For inside valve gear and outside steam chests Mr. von 
Borries advises the use of the American form of the 
Stephenson motion; for inside gear and inside steam chest, 
the Stephenson and Allan types; and for outside gear, the 
Walschaert motion. All of the recent Worsdell engines, 
concerning which information is at hand, are fitted with 
the Joy. valve gear. 


SAE ee Ve 





THE MALLET SysTtEM.—The Mallet system of two-cylin- 
der compound locomotives has been already referred to as 
that in which by means of suitable valves the engine may 
be operated as a simple engine not only in starting, but at 
any time when in service. Such an engine, while having 
all the advantages of compound working, possesses an 
emergency power eyual, or possibly superior, to a simple 
engine having the same general dimensions, 

Figs. 17 to 20, inclusive, illustrate the arrangement of 
this system as applied to a converted six-coupled engine 
of the Western Switzerland Railroad. For the drawings 
from which the illustrations were made, and also for other 
data, I am indebted to Mr. Mallet. The cylinders are 17.7 
and 25.6 inches in diameter by 25.6 inches stroke, one of 
the old cylinders having been retained as the h. p. cylin- 
der. The driving wheels are 58.4 inches in diameter, and 
the working weight, which is all on the driving wheels, is 
79,350 pounds. 

In Fig. 17, h and 7 are the h. p. and L. p. cylinders, re- 
spectively, A is the main steam pipe from the boiler to the 
h. p. cylinder, B is the receiver, Cis the l. p. exhaust 
pipe, Dis the starting valve which is connected to the 
boiler by the pipe EL, F'is the intercepting valve, and G is 
the exhaust pipe from the h. p. cylinder when working as 
a simple engine. 

The construction of the starting valve is shown in Figs. 18 
and 19. It consists primarily of a short slide valvea, 
which, as shown, covers two ports leading to the receiver. 
The pipe p connects the starting valve chamber with the 
main steam pipe. On the back of the valve ais an inverted 
slide valve b, which slides on a seat formed in ‘the valve- 

4 


50 COMPOUND LOCOMOTIVES. 


chest cover. A small pipe c connects the starting valve 
chamber with the intercepting valve, on the other side of 
the smoke box, as shown at c, Fig. 20. Referring now to 
Fig. 20, it will be seen that the intercepting valve consists 
of two circular valves and a piston, all being mounted on 





Fig. 17 


one stem, and so forming a sort of balanced double poppet 
valve. The connections to the intercepting valve are as in- 
dicated in the figure, the central opening connecting with 
the h. p. exhaust, the left with the common exhaust nozzle 
and the right with the receiver pipe. 

The operation of these valves is as follows: They are 
shown in the illustrations in the positions which they 


COMPOUND LOCOMOTIVES. 51 


ordinarily occupy, or when the engine is working as a com- 
pound. Under these circumstances steam from the boiler 
is admitted to the space d back of the piston e by way of 
the small pipe c, the starting valve chamber, and the pipe 
p. The pressure thus acting upon the piston e keeps the 
valve g closed against the ordinary receiver pressure. The 
intercepting valve can, of course, be connected so as to be 
worked by hand in connection with the starting valve. If 
now the starting valve is opened, or moved to the right in 
Fig. 18, steam from the boiler is thereby admitted to the 
receiver, and at the same time the pipe c is placed in com- 
munication with the atmosphere by means of the cavity in 
the top of the starting valve. The pressure back of the 







NSSSININ TS 


i= ey 
Wy GZS 
Vp 


Y 












SSS 


Fig. 18 


piston e being thus reduced, the valve g is opened by the 
receiver pressure, and the valve his closed, in which posi- 
tion it isretained by the excess of the pressure in the re- 
ceiver k, Fig. 20, or that on the l. p. side of the valve, over 
that on the h. p. side, which is now in communication 
with the exhaust nozzle. It will be seen that the loco- 
motive will now work asa simple engine, and will con- 
tinue todo soas long as the starting valve is kept open. 
As soon asitis closed, the intercepting valve will be re- 
turned to the position shown in Fig, 20. 

On the engine illustrated by Fig. 17, a pressure-reducing 


52 COMPOUND LOCOMOTIVES. 


valve is inserted between the starting valve and the re- 
ceiver. This reducing valve is of the common differential 
piston type, adjusted by springs. In addition to this the 
receiver is fitted with a spring safety valve loaded to 70 
pounds pressure. It would seem when a starting valve of 
this form is used in conjunction with a safety valve, that 
the introduction of a reducing valve is unnecessary, as the 
receiver pressure can be regulated by the starting valve. 





In earlier designs Mr. Mallet has combined the starting 
and intercepting valve in one distributing valve. This is 
illustrated by Figs. 21 and 22, which are reproduced from 
Engineering. The distributing valve and a reducing valve 
are enclosed in a casing which is fastened to the smoke 
box. The main steam pipe is connected at a, and thence 
by a passage b, back of the valves, to the h. p. steam chest. 
An opening at c admits steam from this pipe to the reduc- 


COMPOUND LOCOMOTIVES. ; 53 


ing valve chamber and thence to the distributing valve 
chamber. The distributing valve is a slide valve, and 
covers three ports, as shown. Of these d is theh. p. 
exhaust, e connects with the receiver, and hence with the 
1, p. steam chest, and g leads to the exhaust nozzle. The 
valve is shown in the position for compound working. If 
it is moved forward, or to the left in the illustrations, the 
passage d is connected with g, and the h. p. cylinder 
exhausts directly to the exhaust nozzle, and at the same 






Z 
| 


Sb 
ow 


fli 









SS 






Ws 
I 


Fig. 20. 


time by means of the passages c and e boiler steam at 
reduced pressure is admitted to the receiver and the l. p. 
steam chest. 

In the earlier Mallet engines the lifting shaft is divided 
so that the valve motion of each cylinder is to a certain 
extent independent of the other. The h. p. valve gear is 
controlled by a screw and nut, which takes the place of the 
ordinary quadrant. The nut which is on the h. p. re- 

verse lever carries a short sector or quadrant and 


54 COMPOUND LOCOMOTIVES. 


a latch on the 1. p. reverse lever works in this sec- 
tor. The effect is that both cylinders can be re- 
versed by moving the h. p. lever; while by adjusting 

















SEZ = 












I a - 
PYSSSSSSS SONS SSS NSS wy mb 00001 
Y lof 4+ aN NP, 






Z 
De mea 
Y 


y 
Ya) ames) 
W bie a A (eS <a 
(, ny, SZ 
=NN RK SSSR 
eae gu0o0 
RY Viana 


— IS N 

N 

ON 
meq 






































Fig. 21 
ai Coe 
ce ays WLLL ZL YIU 
a Ne 


Cal 


SPspsLZ 








le \ ar SET 
pk rhs Ss 
( once ment wee 
8% 
















ere ___e Oe SIF A 
NSS WES —<<—\— 















N 


(eee 





the 1. p. lever, the cut-off in that cylinder may be made 
either later or earlier than that in the h. p. cylinder. It is 
obvious that the same principle can be applied to the type 


COMPOUND LOCOMOTIVES. 5d 


of reversing gear common in this country by connecting 
the h. p. valve gear as at present, and connecting the l. p. 
reverse lever to the h. p. lever by means of an auxiliary 
quadrant carried by the latter. A device for tripping the 
latch of the 1. p. lever might be advisable, so that the h. p. 
lever could be moved between the two extremes in both 
directions without regard to the position of the 1. p. lever. 
It is, however, by no means proven that it is necessary or 
advisable to have two reverse levers, and, in fact, the 
weight of evidence appears to be to the contrary. 

For the locomotive illustrated in Fig. 17, Mr. Mallet has 
adopted a differential motion for the purpose of obtaining 
a later cut-off in the 1. p. cylinder in both forward and 
backward gear. The principle of this motion is illustrated 
by Fig. 23. In this Fig., is the lifting shaft and B is an 
auxiliary shaft. The lifting arm M of the h. p. link and 
the arm Care keyed to the lifting shaft, while the 1. p. 
lifting arm N and the arm H are in one piece, which turns 
about this shaft. The slotted arm D and the arm £ are 
keyed to the auxiliary shaft. The arm C carries a block 
which slides in the slotted piece D. The parts are shown 
in the Fig. in a position for backing, the 1. p. link being 
raised higher than the h. p. link and therefore cutting off 
later. In full backing gear the arms Mand N would be 
paralle] and hence give the same cut-off in both cylinders. 
In mid-gear the arms C and D are on the center line A B, 
while in forward gear, or to the left in the Fig., the lifting 
arm N is lowered more rapidly than the arm M. Mr. Mallet 
gives the following as the distribution obtained with this ar- 
rangement : 


Forward Gear. Backward Gear. 
High-pressure cylinder... .70 .60 .50 .40 .30 .0 0 .60 .70 
Low-pressure cylinder... .70 .65 .60 .55 .50 .0 ss 65%, 370 


STEAM PASSAGES.—It would seem to be an unquestion- 
able principle of steam engine design, that all steam 
passages should be large and as free from abrupt bends 
and contractions as it is possible to make them, and 


56 COMPOUND LOCOMOTIVES. 


should be so placed and protected that the loss by radiation 
will be reduced to.a minimum. With these principles in 
view, there appears to be room for improvement in the 
designs of many existing compound locomotives in one or 
more particulars. 

The proportional areas of steam ports in the two-cylinder 
compound locomotives which have been examined are 
somewhat less than in recent American locomotives. Mr. 
von Borries recommends areas which, for a cylinder ratio 
of two, would be about 8 to 8.2 per cent. of the piston area 
for the high-pressure, and 7 per cent. for the low-pressure 
cylinder for passenger engines. For freight engines having 
slower piston speeds, the areas may be 10 per cent. less. 
Mr. Worsdell’s practice for both passenger and freight 
engines appears to be 8.1 per cent. for the high-pressure 
cylinder, and about 6.4 per cent. for the low-pressure. 
These proportions give for cylinders 18 and 26 inches 
diameter by 24 inches stroke; high-pressure steam ports, 
12 by 114 inches ; low-pressure steam ports, 2 by 17 inches; 
exhaust ports, 34 inches wide and of the same length as the 
steam ports. 

The volume of the receiver should not be less than that 
of the h. p. cylinder, and preferably should be larger than 
this, in order that the fluctuation in the h. p. back press- 
ure may be as small as possible. Also in engines of the 
Worsdell and von Borries type a large receiver will permit 
a more satisfactory action in starting than a small one, as 
more time will be required to compress the exhaust steam 
from the high-pressure cylinder to the pressure necessary to 
open the intercepting valve, For engines of ‘‘ ordinary size” 
Mr. von Borries gives 200 mm. (74 inches) as a suitable 
diameter for the receiver pipe, with a thickness of about + 
inch when made of copper. 

SLIDE VALVES.—The most noticeable difference between 
the distributing valves of compound and ordinary locomo- 
tives is in the large inside clearance of the former. This is 


COMPOUND LOCOMOTIVES. 57 


made necessary by the high pressure of the back pressure 
line of the h. p. cylinder, and the consequent necessity of 
securing a late exbaust closure in order to avoid excessive 
compression in that cylinder. For the l. p. cylinder there 
are similar requirements, as, with the same back pressure 
as in simple locomotives, the pressure at the end of compres- 
sion should not exceed that in the receiver. The necessary 
changes from the ordinary valves may perhaps be best 
illustrated by giving a few examples of the proportions 
which have been adopted : 


Width of Outside Inside 
port. Travel. lap. clearance. Lead. 
{ IGREAES oh a eva'e e's 505 13 514 1% 4 rr 
Dk ae 514 48 6 Ps 
} Pe Ong v's oe 13% 5% 1% yy =e 
is 1S rr 5% 1% % =e 
ith CONG a 1.6 3* 1.4 3 pal 
i PE tate ee no.60 8s 3 1.4 0.0 oF 
j ES Siac oi 0 3° 1.35 2.65 1.3 .26 Ai 
MPa tiv ay as «508 1.44 2.58 1.15 0.0 .06 
i EA oe ree tv's ose ss 4,2 1,12 25 02 
lon DS bo 1.16 4.5 1,12 0.0 — .03 





* Mid-gear travel. These dimensions are advised by Mr. von 
Borries. 


These dimensions are given simply as illustrations, as of 
course the proper dimensions for any engine can only be 
determined satisfactorily by the use of a model, or by 
drawing the motion to fullsize. In either case adjust- 
ments by the indicator should follow, as the economy 
of the engine will depend very largely upon the care and 
attention given to the steam distribution. 

SIZE OF CYLINDERS—TRACTIVE POWER.—A compari- 
son of existing compound locomotives and of the rules sug- 
gested by different writers, shows about as much dif- 
ference of opinion as to the proper proportions of cylin- 
ders, boiler pressure, driving wheel diameter and adhesion 
weight, as was found in ordinary locomotives by the com- 
mittee of the Master Mechanics’ Association on the subject 
in 1887, 


58 COMPOUND LOCOMOTIVES. 


The following is translated from the fourth edition (1888) 
of Mr. von Borries’ pamphlet on Compound Locomotives : 
‘“‘To compute the size of the cylinders, we suppose, for 
the sake of simplicity, that the whole work is to be done in 
the large cylinder, the diameter of which is then computed. 
2ZD 

ph 

diameter of the 1. p. cylinder; Z = the required tractive 
force = 0.15 of the adhesion weight (where allowance is 
made in Z for the external engine friction, taken as equal 
to that for cars); D = the diameter of the driving wheels ; 
p = mean effective pressure (after deducting internal ma- 
chine friction); h = stroke of piston. The value of p de- 
pends upon the relative volumes of the two cylinders, and 
from experiments, and indicator cards may be taken from 
the following table : 


by the following formula: d? = . In which d = the 





Ratios of p for 176 Ibs. 

cylinders. boiler pressure. 
Large locomotives withtenders. 1:2to1:2.05 741bs. (42 per cent.) 
Tank lOCOMOLIVOS: a. unio weritetni 1:2.15 to 1:2.2 71 1bs. (40 per cent.) 


For locomotives for roads having many and long grades 
a larger co-efficient of adhesion (Z = 0.16) is to be used, to 
obtain larger cylinders ; but 0.15 is ordinarily sufficient.” 

“* For compound passenger and express locomotives, the 
diameter of the large cylinder may be made 1.5 that of the 
cylinders of the ordinary locomotive for the same service, 
the steam pressure being at the same time increased 15 to 
30 pounds. This is based upon the supposition that 
the ordinary locomotive is properly proportioned. 
The working conditions should also be kept in view, so 
that the locomotives may work as much as possible at the 
more economical points of cut-off of 0.3 to 0.4 in the small 
cylinder.” 

For a passenger engine of 57,300 pounds on the driving 
wheels, Mr. von Borries gives the cylinder dimensions as 
16.5 and 23.6 inches in diameter by 22.8 inches stroke, and 
says that such an engine will accomplish 10 to 15 per cent. 


COMPOUND LOCOMOTIVES, 59 


more than a common locomotive having about the same 
heating surface. 

The following statement is made in the paper by Mr. 
Lapage, from which I have already quoted: ‘It is cus- 
_ tomary, when not otherwise specified, to make the size of 
the high-pressure cylinder the same as that of the cylinder 
of an ordinary locomotive. Such engines are found to 
haul from 5 to 10 per cent. heavier trains, while saving 
about 10 per cent. of fuel.” 

In a paper on ‘‘ The Compound Principle as Applied to 
Locomotives,” read by Mr. Edgar Worthington in January, 
1889, before the Institution of Civil Engineers, we find it 
stated that the high-pressure cylinder should be made 
about one inch larger in diameter than the cylinders of an 
ordinary engine of equal power, even though an advance 
of 30 pounds per square inch of boiler pressure was con- 
templated for the compound engine. 

The difference of opinion among designers may perhaps 
be best illustrated by a short table. 


Diameter by 





Weight aes eed 
1 + i ie on e 
on driv- Rie ee Stroke ** Taches. 2é |3¢ 
ing | wheels. | 58S Te-lTn ches, nS Sad 
wheels. | Tnohes, | Pounds. Se. a aa 
go | 5k 
Ome | Skim 
footie Lage) > q 
57,320 73.2 176 22.8 17.3 24.8 27.3 17.5 
57,300 68.1 176 22.8 16.5 23.6 26.4 16.9 
88,250 52.4 174 24.8 18.1 25.6 27.6 Lice 
80.25 170 24.0 18.0 26.0 30.9 19.8 
40,320 85.25 175 24 0 18.0 26.0 24.2 15.5 
; 61.25 160 24.0 18.0 26.0 32.0 20.3 
101,600 61.25 160 24.0 18.0 26.0 34.0 21.8 
46,48 42.5 160 21.6 10.6 17.0 20.2 13 0 
AS 60.00 120 24.0 18.0 24.0 *16.0 
79,350 58.4 140 25.6 47.7 25.6 30.4 19.5 


* Original diameter, simple engine. 


60 COMPOUND LOCOMOTIVES. 


In the last column of the table are given the diameters 
of cylinders for simple locomotives having the same boiler 
pressure, adhesion weight, and diameter of , drivers, calcu- 
lated by the Master Mechanics’ formula. In the col- 
umn preceding this are given the diameters of the 
low-pressure cylinders calculated by the von Borries 
formula, as already quoted. It will be seen that this for- 
mula gives, in general, larger results than are found in 
practice. The same formula, as quoted in the 1886 edition 
of ‘‘Recent Locomotives,” contains values for Z and p, 
which will give diameters about 7 per cent. smaller 
than with those quoted above, which indicates that Mr. 
von Borries has concluded that larger cylinders are ad- 
visable. 

It appears to the writer that no general rule can be de- 
vised which would be applicable to all cases, and that the 
character of the work which is to be required of the com- 
pound engine, as shown by a study of the work done by 
the simple engine which it is intended to replace, is the 
only safe guide. The maximum and minimum limits of 
mean pressure between which the engine will probably 
work, the usual demand upon it as determined by the 
character of service, and the type of starting device which 
is to be employed, must all be given consideration. In 
brief, if full advantage is to be taken of the economical 
possibilities of the compound locomotive, the first requisite 
in attempting its design is a thorough understanding of 
what it is expected to do. 

The most satisfactory method of comparing the work 
done by simple and compound locomotives is a comparison 
of indicator cards taken from the two forms of engines 
under the usual working conditions. Complete sets of such 
cards from compound locomotives have not been obtain- 
able, but a sufficient number of cards are included in 
the accompanying table to make it of some value. The 
figures given for the compound engines were selected 


COMPOUND LOCOMOTIVES. 61 


principally from reports of the performance of various 
two-cylinder engines which have appeared from time to 
time in foreign technical journals, and may be assumed to 
be at least a not unfavorable representation of their capa- 
bilities. For the simple engines cards have been selected, 
which were taken at nearly the same number of revolutions 





COMPOUND. SIMPLE. 


























' 2 ° ° s : ee oO e e ' 

o 18 |e |e) ei ge ig lag jae | € 2 

ale IB |4alale (2 “ale 8 2 

a |e Sey ona ae eo 2 |S 

No. |e, o|mt & : NH -|\oAn| An | 

Pe\Ss/Sa) 9) 9) gd lagless|>33 $9 | 9 |8s 
ofSshad/ |) 8] 84 |Sq'SASIdES| SA 8 Ss 

S18 mi DlOlha la la (a) | (b) | O |Q 
i Dol rete 27; 170} 160) .73) .86) 109.0/53.0} 110.0) 105.0) 121 eee CES 
2 _| 42] 170] 170| .70) .85| 106.6/43.0| 89.4] 98.0) 122.0, .71| 148 
8...0222-| *a7| 162] 160! .70) .73| 92.2/44.9) 89.8] 91.0) 119.0) .75| 146 
Eee *74| 173) 165) .60| .65) 75.6|37.1| 74.2) 74.9) 111.0)....| 139 
5...e.2.-| 114/ 170) 154) .50} .60} 89.4/45.1) 91.5} 90.5! 85.0)....| 130 
Grae... .| *80| 162) 150] .60| .65] 68.3/37.3| 74.61 71.4} 96.0, .46| 146 
7....----| 135} 170) 138] .5u| .60| 60.9/35.3! 71.7) 66.-| 101.0] .58) 140 
yeh Status: *128| 176] 132} .80) .80) 65.3/31.7| 63.4) 64.3) 80.0) .46| 140 
9........| 147| 170] 160! .50| .73| 67.5/29.8| 62.0} 64.7] 62.0] .34/ 130 
Hy Bees 120} 162) 157] .50| .50) 57.2/33.2} 83.0) 70.0) 60.0] .42) 130 
ieee 150} 168} 143) .30! .40) 46.7/29.4| 59.7) 53.2) 59.5) .42| 135 
5 hae ee 161| 176) 162} .30| .40 52.0 26.7 54.5} 53.2) 53.0} .34| 130 
Li ear ee 161} 176) 166) .40) .50) 62.9/33.6) 68 5) 65.7] 58.5] .33] 138 
Nae See 162) 177) 145] .40) .50| 61.4/36.3) 73.7) 67.5) 75.6] .42) 128 
UE Sede 171| 176) 152}; .20) .30} 47.0/23.9|} 48.8] 47.9) 53.8] .29) 136 
RG ees 180} 172) 131) .30| .40) 48.2/28.9) 58.7] 53.4) 59.0] .38] 144 
Viete: 195) 170) 141} .40) .50| 53.9/27.6| 56.0) 54.9} 53.5] .36] 136 
TSosee ece| 209). 160) 147). .50| .73| . 56.5/26.0) 54.1). 55.3) 52.0) .29) 148 
By ee c kote 230) 175) 148] .75|....) 55.7/24.8) 516) 53.6} 49.2] .36} 137 
ue 41.1/19.2} 39.9) 40.5! 43.0) .36) 135 





* Rev. of simple engine; speed of compound not known. 


as those of the compounds, in order to eliminate the ques- 
tion of speed as far as possible. For convenience in com- 
paring the mean pressures in the two types of engines, the 
average of the h. p. mean effective pressure and that in 
the |. p. cylinder referred to the h. p. cylinder is given in 
column (a). It is, of course, not to be assumed that the 


62 COMPOUND LOCOMOTIVES. 


figures given in the same line necessarily represent the 
best that either engine can do, and isolated examples form 
no basis for argument, but a comparison of columns (a) and 
(b), together with the points of cut-off, clearly shows some 
of the advantages and disadvantages of the compound as 
compared with the simple system. It is to be borne in 
mind that the results given in the table for compound loco- 
motives represent compound working in all cases, and not 
their capacity when working as simple engines by means 
of starting or distributing valves. The question of starting 
power will be discussed subsequently. 

The table shows that the maximum average mean 
pressure of the compound is less than that readily attain- 
able.in the simple engine at slow speeds and late cut-offs. 
For example, in line 2 of the table, the points of cut-off 
- being nearly identical, the compound gave an average 
mean pressure of 98 pounds, with 170 pounds boiler press- 
ure, as against a mean pressure of 122 pounds for the simple 
engine, with 148 pounds boiler pressure. The compound 
is evidently deficient here, and it is necessarily so. The 
total possible range of pressure in the two cylinders is from 
170 pounds to the atmospheric pressure. If there were no 
losses and the full initial pressure could be maimtained 
throughout the h. p. stroke, the maximum mean pressure, 
assuming two as the cylinder ratio and an equal division of 
work, would be two-thirds of 170 in the h. p., and one- 
third in the 1. p. cylinder, or about 113.38 and 56.7 pounds 
respectively. These are the maximum mean pressures at- 
tainable with 170 pounds boiler pressure. It follows di- 
rectly from this that if it is required that the compound 
shall have tractive power equal to that of the simple en- 
gine in this case, the area of the high-pressure piston 
would have to be greater than that of the simple engine, 
in the proportion of about 122 to 100, even though the 
boiler pressure be increased 20 pounds. 

On the other hand, a further inspection of columns (a) 


COMPOUND LOCOMOTIVES. 63 


and (b) shows that at the earlier points of cut-off and 
higher speeds, the compound engine is about equal to the 
simple engine, from which it follows that a high-pressure 
cylinder of the same size as one cylinder of the simple 
engine would be sufficient. The correct size for the h. 
p. cylinder is undoubtedly somewhere between these 
two limits ; for if designed for the power necessary at high 
speed it will probably be deficient at slow speed and late 
cut-off ; and on the other hand, if made large enough to 
meetall emergencies, the engine will be over-cylindered 
for ordinary running. If over-cylindered, the effect will 
be that, when the only work required of the engine is to 
maintain the speed on level parts of the road, the necessary 
mean pressure will be obtained with an earlier cut-off than 
is advisable with the common forms of valve gear, and asa 
resultof the large ratio of total expansion, the final press- 
ure in the 1. p. cylinder wiil be very low, possibly below the 
atmospheric pressure. The conclusion which seems evident 
is, that in designing a compound to take the place of a 
simple locomotive, the basis for calculation should be, as 
has been already stated, a detailed record of the work done 
by the simple engine, taking into account the number and 
rise of grades, the variation in weights of trains, and the 
frequency of stops. 

The table also shows clearly one of the causes of the 
economy of the compound locomotive. Comparing lines 
11 to 17, inclusive, we find that the average mean effective 
pressure of the compound engines is 56.5 against 58.7 in 
the simple engines, the average cut-off being .33 in the 
h. p. cylinder of the compound and .36 in the simple engine. 
It appears from this that the compound engine will do 
the same work with about one-half the volume of steam. 
This is not, of course, a measure of the economy, but it is 
an indication of one of the causes of the economical per- 
formance of compound locomotives. 

In the National Car and Locomotive Builder of Sep- 


64 COMPOUND LOCOMOTIVES, 


tember, 1889, were given a number of indicator cards 
which serve admirably, in connection with data given in 
the accompanying description, as an illustration of the ap- 
plication of the principles of design just discussed. Partic- 
ulars are given of twenty-seven cards, for which the speec 
ranges from 120 to 312 revolutions, and the mean effective 
pressures from 71.3 to 41.8 pounds, the average mean effec- 
tive pressure being 49.8 and the mean cut off about .384. The 
engine was hauling the New York and Chicago Limited, 





and only one stop was made between New York and 
Albany. Anexamination of the above table indicates thata 
two-cylinder compound locomotive having a high-pressure 
cylinder of the same size as a cylinder of the simple 
engine, and with 170 or 175 pounds boiler pressure, could 
haul this train under ordinary circumstances without dif- 
ficulty, the only additional requirement which is apparent 
being the adoption of some form of starting valve which 
will insure a starting pressure of about 122 pounds in the 
h. p. cylinder and its equivalent in the l. p. cylinder. This 
appears to be a very simple case, the principal remaining 


COMPOUND LOCOMOTIVES. 65 


question being, how often would the engine be required to 
develop more power than is shown by these indicator cards ? 
The records of the road should furnish the answer which 
will indicate whether it is necessary or not to increase the 
size of the cylinders, and if so, the amount of such increase, 


CHAPTER V. 





STARTING POWER OF TWo0-CYLINDER COMPOUND LOCO- 
MOTIVES.—So much has been written on this subject, and 
so little has been really logically demonstrated, that it may 
be well to first briefly investigate the starting power of 
locomotives of the ordinary form in order to compare the 
two systems intelligently. 

It is the almost universal practice to measure the trac- 
tive power of locomotives by applying the formula, 


Y= ons + *in which d = the diameter of the cylinders in 
inches, p = the mean effective pressure in pounds per 
square inch, s = the stroke in inches, D = the diameter of 
the driving wheels in inches, and T = the tractive power 
or pull at the railin pounds. This formula is based upon 
the fact, that, neglecting friction, the work done in both 
cylinders during any period, such as one revolution, is 
equal to that done at the circumference of the driving 
wheels during the same time. The work done in the cyl- 
inders in inch-pounds is 2 X area in square inches X mean 
effective pressure xX twice the stroke in inches = 2 X 4 
xd? X p X 2s.; that at therim of the driving wheels is 
the pull in pounds x the circumference of the wheel in 
inches = 7 x 2 D; therefore, 
a Xi ede ie Oya pe 
nx D REP avis bya 

It follows from the method of deduction that this formula 
gives an average value for the pulling power, and therefore 
that, while it furnishes a ready method of comparing the 
pulling power of locomotives under ordinary conditions, 
itisof very little use in estimating the starting power, 





hk, ee 





COMPOUND LOCOMOTIVES. 67 


since the minimum pull, and not the averuge, is then the 
measure of the power of the locomotive, 

In the ordinary locomotives, assuming that steam can be 
admitted during the full stroke, and neglecting the effect 
of angularity of connecting rods, the minimum pull oc- 
curs when one crank is on the haif center, the other being 
at a dead point, and the maximum pull is developed when 
both cranks make an angle of 45 degrees with the center 
line through the dead points. This can be readily demon- 
strated by calculation, or by a graphical construction. 
There are several methods of representing rotative efforts 
graphically, one of which is shown by Fig. 24, in which 








1 i ' | 
! NI | i : 7 | 

on j ne, 4 ! 
: mee | le PH Dg yg, eo 
I ie Xa ae, Le ee aio 4 
WA es tN Suk \I7 N 
A % %JS% % % % % % B 

Fig. 24 


the dotted line a. . a represents the rotative effort, or the 
tangential pull or push, on one crank pin, and b. . b is that 
of the other at right angles to it, the steam pressure being 
assumed as constant throughout the stroke. The 
method of construction is as follows: Let A B be 
the length of the circumference of a circle, of which C D, 
Fig. 25, is the radius. It can be readily shown that the 
component D F, of the pressure on the piston D H, which 
tends to produce rotation, is proportional to the sine of the 
angle a, through which the crank has turned from a dead 
point. Divide the line A B and the circumference in Fig. 
25 into the same number of equal parts. Then through the 
points of division on A B lay off perpendicular distances, 
such as kd, equal to the lines which represent the sines of 
the angles in Fig. 25, such as K D. 


68 COMPOUND LOCOMOTIVES. 


The dotted curve aa represents the variations in rotative 
efforts on the crank starting from C Z during one revolu- 





tion, and the curve b b, shown by a broken line, represents 
the variations in efforts on the crank starting at C M, or at 
right angles with the first. The total rotative effort is 
shown by the ordinates of the full line curve in Fig. 24, 
which is obtained by adding the ordinates of the curves 
for the single crank, for example,fm=fg+fh. It is 
evident that the value of the total effort varies between 
ANandke,. In the first case, one crank is on a dead 
point, and the other is on the half center, or midway be- 
tween the two dead points. The pull at the rail is then 
¢ zd? Xp X s+ D, which is .7854 of the tractive power 
as found by the ordinary formula. In the second case the 
pull is twice that of one crank when making an angle of 
45 degrees with the center line, or it is } 7d? Xp X2X 
.707%s + D, which is 1.11 of the tractive power as usually 
estimated. Itis also clear that there are four maximum 
and four minimum points during a revolution. These 
values are determined, as has been said, on the basis that 
a constant steam pressure can be maintained throughout 
the stroke, which would be the case in starting if steam 
could be admitted to the cylinder during the whole stroke. 
But when the latest cut-off takes place, when the piston is 
some distance from the end of the stroke, as, for example, 


COMPOUND LOCOMOTIVES. 69 


at 21 inches with 24 inches stroke, the engine may be ina 
worse position for starting than that given above as a 
minimum, When one piston is 21 inches from the be- 
ginning of its stroke the other will be about four inches 
from the beginning of its stroke, and its crank will have 
turned through about 50 degrees from a dead point. If 
cut-off takes place at 21 inches, no steam can be admitted 
to that cylinder during the remainder of the stroke, and 
the work of starting devolves upon the other cylinder. 
When the piston has moved four inches from the be- 
ginning of the stroke the rotative effort is about three- 
fourths of the maximum for one cylinder, and is, there- 
fore, about .589 of the tractive power as usually estimated. 
This corresponds to an ordinate of the curve a a, a little to 
the right of k d, and is evidently the most difficult posi- 
tion from which to start the ordinary locomotive. The re- 
duction in the rotative effort on account of the fall in 
pressure due to the expansion after cut-off and release 
will be slight. It can be shown on the diagram by laying 
off radial distances such as C Pand C R on the proper 
radii to represent the pressures for these crank positions, and 
using the lines PQ and RF S for ordinates in Fig. 24 instead 
of those used before. The final effect is shown by the 
dotted curve at n, Fig. 24. 

As the locomotive starts the mean effective pressure in 
the cylinders will be somewhat reduced, but the reduction 
will not be of large amount within what may be called the 
starting limits, or until the link would ordinarily be 
hooked up. As the speed increases the inertia of the 
reciprocating parts, etc., will be sufficient to modify the 
form of the diagram of crank efforts, but it is not necessary 
to consider that in estimating the starting power. 

Turning now to the compound locomotive, it is apparent 
that in the Mallet system the starting conditions are almost 
identical with those in the simple locomotive. If the h. p. 
cylinder is of the same size as one cylinder of the simple 


70 COMPOUND LOCOMOTIVES. 


locomotive, and the cylinder ratio is two, it is only neces- 
sary to admit steam of one-half the boiler pressure to the 
1, p. cylinder in order to have starting power equivalent to 
that of the simple engine, the same boiler pressure being 
used. If thel. p. initial pressure is greater than one-half 
the boiler pressure, the starting power of the compound will 
be greater than that of the simple engine in all positions in 
which the I. p. cylinder is available for use in starting, that 
is, except when the l. p. crank is on a dead point, or when 
the l. p. valve is in such a position that steam cannot be 
admitted. If the boiler pressure of the compound is higher 
than that of the simple engine, and the h. p. cylinder is 
the same size as one of those of the simple engine, the 
starting power of the compound engine will be the greater 
in about the proportion of the two boiler pressures. 

In the Worsdell and von Borries type of compound loco- 
motive the conditions in starting are quite different from 
those just described. When steam is admitted to the re- 
ceiver by means of the starting valve, the intercepting 
valve is closed, and the h. p. piston therefore starts 
against the pressure of the steam or air which filled the 
receiver just before the starting valve was opened. The 
amount of this receiver pressure will depend upon the 
length of time during which the engine has been standing, - 
the condition of valves, etc. Ifat starting the h. p. crank 
is at a dead point, the pencil of an indicator, which is ap- 
plied to the steam end of the h. p. cylinder during the first 
stroke, will trace a line similar to abe, Fig. 26. The 
back pressure acting against the other side of the piston 
during this stroke is shown by a line such as d e, the press- 
ure at e being somewhat greater than that at d on account 
of the compression in the h. p. cylinder and receiver. The 
initial back pressure is assumed in the present case as 
equal to the atmospheric pressure. The diagram, a bced, 
thus represents what may be called the effective indicator 
card for the first stroke of the h. p. piston. 


COMPOUND LOCOMOTIVES. 71 


When the h. p. exhaust opens the pressure in that cyl- 
inder and the receiver will fall to some point g, which can 
be only approximately determined by calculation. It is 
located on Fig. 26, by calculation on the basis of no conden- 





Fig. 26 


sation or evaporation during the exhaust. The forward 
pressure on the h. p. piston during the second stroke will be 
similar to that during the first stroke, and is shown in Fig. 
26 by hkl. The back-pressure line during this stroke will 
consist of, first, a curve g m, which represents the com- 
pression by the h. p. piston of the steam which fills the 
space between the h. p. piston and the intercepting valve, 
until that valve opens; and second, of a line m n, of nearly 
constant pressure, which represents the back pressure dur- 
ing the remainder of the stroke, after the intercepting 
valve opens and the starting valve is closed. It is generally 
stated that the pressure of the steam, which is admitted di- 
rectly to the receiver in startihg is reduced by wire draw- 
ing to about one-half the boiler pressure. Assuming this 
to be correct, the h. p. back pressure will become sufficient 
to open the intercepting valve when about five-eighths of 
the second stroke has been accomplished, as indicated at 
m, Fig. 26. The net diagram from which the effective 
pressure on the h. p. piston for the second stroke can be 
obtained is then hklnmg. A diagram of rotative 
efforts constructed from these indicator cards is shown in 


72 COMPOUND LOCOMOTIVES. 


Fig. 27 by the curve A EF C FB, from which the reduced 
effort resulting from the increasing back pressure during ~ 
the second stroke is apparent. 

The distribution of work in the 1. p. cylinder in starting 
does not differ from that in the simple engine. The rota- 
tive effort will, therefore, be represented by a curve such 
as H K L D M, Fig. 27, which has the same form as the 





single crank curves in Fig. 24. The curve in Fig, 27 is 
constructed on the basis of the initial 1. p. pressure, being 
one-half of the boiler pressure. If the initial pressure is 
greater than this, the ordinates of the curve between H 
and K, K and D, etc., should be proportionately increased. 
The combined effort of the two cylinders is shown in Fig. 
27 by the full line curve. The intercepting valve opens at 
about the point /, and from that point the engine will work 
asa compound. It has been already shown that when 
so working with the customary pressures the power 
developed at late cut-offs is less than that of the simple 
engine. The location of the point at which the intercepting 
valve opens depends upon the pressure in the receiver 
before starting, the pressure of the steam admitted to the 
receiver by means of the starting valve, and the size and 
location of the receiver. For any given combination of 
conditions it will be found at a definite distance from the 
point C, or from the end of the first stroke of the h. p. 
piston. In the present case this point was found to be 
about five-eighths of the stroke from C. It is obvious that 


COMPOUND LOCOMOTIVES. uo 


this action is not at all dependent upon the first stroke of 
the h. p. piston, but only upon the exhaust from that cyl- 
inder. It follows from these considerations that, if the h. 
p. crank is at a dead point at starting, the engine will move 
through something over three-fourths of a revolution be- 
fore compound working begins; but, on the other hand, 
if the h. p. piston is at the position corresponding to P, or 
near the point at which cut-off takes place, the compound 
working will begin after about seven-sixteenths of a revolu- 
tion. If theh. p. crank is in some position such as Q, at 
which the steam valve is closed, the starting must be ac- 
complished by the 1. p. cylinder_alone; but after a slight 
movement, sufficient to carry the h. p. crank over the dead 
point, the cycle will continue as if started at A, the effect 
being to prolong the time of direct working of the I. p. cyl- 
inder to about seven-eighths of a revolution. 

After compound working commences, and while ad- 
mitting steam for as much of the stroke as possible, the 
combined diagram of rotative efforts would be similar to 
Fig. 24, but with a smaller mean effective pressure, the 
proportion being with boiler pressures of 170 and 150 
pounds in the two types, not greater than 110 to 122, as has 
been already mentioned. The two diagrams Figs. 24 and 
27 are not drawn to the same scale of pressures, but the 
shape of the full line curves represents with reasonable 
accuracy the variations in rotative efforts in the simple 
and compound locomotives. In conclusion, it appears 
that, with the pressures customary in the two forms, the 
pulling power of the Worsdell and von Borries’ type of 
compound locomotive in starting may be greater than that 
of the simple engine having cylinders of the same size as 
theh. p. cylinder, during the first half revolution ap- 
proximately, but that after this the power of the compound 
engine diminishes until it is from eighty to eighty-five per 
cent. of that of the simple engine. 

There is another type of two-cylinder compound locomo- ° 


44 COMPOUND LOCOMOTIVES. 


tive which has not as yet been described in these pages and 
for which somewhat different conditions exist in starting. 
In this form the marine practice is followed of placing a 
valve or cock on the receiver, by which steam from the 
boiler can be admitted to the receiver and the 1. p. steam 
chest, without the addition of intercepting valves or other 
complications. This arrangement was applied to a two- 
cylinder compound locomotive in India by Mr. E. W. McK. 
Hughes, in 1882, and isin use in Germany in a modified 
form known as the Lindner starting valve. The latter is 


-_———~—. 
-_ —— 
- ~~. 




















ee 


— 













































ee ae 





























| ill 
| 


| 




























Yt || 
UL 
AVY 


N 








, WUdddddddddidirrrerrés 


Fig. 28 


illustrated by Fig. 28, which is reproduced from the Rail- 
road Gazette. In Fig. 28, C is the receiver, # is a small 
pipe connecting the receiver and the main steam pipe, and 
J is the starting valve, which has two ports, H and J, 
formed in it at right angles. The lever K by which the 
valve is operated is connected to the reach rod, and the 
proportions are such that K turns through ninety degrees, 


COMPOUND LOCOMOTIVES. %5 


as indicated in the figure when the reverse lever is moved 
from one extreme position to the other. The effect is that 
steam from the boiler is admitted to the receiver when the 
valve motion is in either the extreme forward gear or the 
extreme backward gear, and that the cock is closed for 
intermediate positions. Another feature of the Lindner 
system is the introduction of two small ports, each having 
an area of about 0.17 square inch, in the high pressure 
slide valve, which are so located that when the valve covers 
the steam port, as after cut-off takes place, that end of the 
cylinder is connected by means of one of these small ports 
with the exhaust side of the valve and thus with the re- 
ceiver. The effect is to admit steam at low pressure to the 
end of the h. p. cylinder, which is covered by the slide 
valve, and as the other end is then open to the exhaust and 
hence to the receiver pressure, the pressure on the two 
sides of the h. p. piston is partially equalized. In other 
words, the effective back pressure on the h. p. piston is more 
or less reduced, so that it offers little resistance in starting. 
This device is, of course, useful in starting only for the 
piston positions between full gear cut-off and the end of the 
stroke. 

The possible effect of this arrangement of starting gear 
will depend upon whether or not a safety valve is provided 
to limit the maximum pressure in the receiver. If this re- 
ceiver pressure is equal to one-third of the boiler pressure, 
with a cylinder ratio of two, the effect of the starting valve 
is to enable the engine to start with very nearly the same 
distribution of pressures on the pistons as would be found 
when it is working as a compound in full gear. The re- 
sulting rotative efforts will then be represented by a curve 
such as the full line curve in Fig. 24, the ordinates or actual 
pressures, however, being less than those for the simple 
engine in about the proportion of 113 to 150, with boiler 
pressures of 170 and 150 pounds. 

If the receiver pressure is allowed to become higher 


76 COMPOUND LOCOMOTIVES. 


than one-third the boiler pressure, the back pressure on the 
h. p. piston is increased proportionately, and the result is, 
that the power of the h. p. cylinder is reduced, while that 
of the l. p. cylinder is increased. The advisability of using 
the higher pressure depends upon the positions of the cranks 
at starting. Ifthel. p. crank is at a dead point, the maxi- 
mum effort will be obtained by not admitting any steam to 
the receiver at the instant of starting, but before the en- 
gine has made one-eighth of a revolution pressure in the 
receiver will be necessary to enable the 1. p. piston to act. 
The other extreme is when the h. p. crank is at a dead point 
in starting. When this is the case, the l. p. crank being 
then on the half center, full boiler pressure could be ad- 
vantageously used in the 1. p. cylinder, with the result of 
obtaining a rotative effort about four times as great as ina 
simple engine s.arting with the same crank positions. But 
similarly to the first case, the receiver pressure should be 
reduced almost as soon as the engine begins to move, or 
else the h. p. piston will be practically thrown out of ac- 
tion, and the engine might be stalled after making one- 
fourth of a revolution. 

It appears, then, that with this starting valve and a 
properly loaded safety valve the starting is very simple; 
but the power is less than that of the simple engine having 
cylinders of the same size as the h. p. cylinder of 
the compound, the boiler pressures being 170 and 150 
pounds, respectively. With no safety valve, the utility of 
the device depends upon the position of the crank and the 
judgment of the engineman, and to this it should be added 
that the 1. p. cylinder, piston, rods, etc., must be made 
strong enough to bear the full boiler pressure. 

It is evident that each of the several types of starting 
arrangements has decided advantages and disadvantages, 
With the Mallet type considerable complication seems un- 
avoidable, but the cylinders can be proportioned for the 
usual work on the road, and the engine will nevertheless 


COMPOUND LOCOMOTIVES, 77 


be very powerful in starting. With the Worsdell and von 
Borries type there is also complication, and the engine if 
- proportioned as above will be powerful at the start, but 
the power rapidly decreases. The Lindner type has the 
advantage of great simplicity, but the cylinders must 
be considerably larger than for a Mallet engine of equal 
starting power. 

CONDENSATION IN CYLINDERS.—It is not intended to dis- 
cuss under this heading the effects of initial condensation 
and re-evaporation during expansion and during exhaust, 
but rather to call attention to some of the special require- 
ments of the compound locomotive in this connection. It 
has been repeatedly shown by writers on compound en- 
gines that the loss from condensation should be less in the 
compound than in the simple engine, under similar condi- 
tions, but the gain in this direction may be more than 
overcome by faulty mechanical arrangement. That is to 
say, if the cylinders, steam passages and receiver are poorly 
protected from losses by radiation, the doss by condensa- 
tion may become sufficiently great to seriously diminish 
the theoretical thermal advantages of the compound en- 
gine. 

When steam which is initially dry is expanded in a non- 
conducting cylinder, or without gain or loss of heat, a par- 
tial condensation takes place, and the greater the range of 
pressure is during expansion, the greater will be the con- 
densation. As the transfer of heat between the steam and 
the cylinder walls is less in the compound than in the simple 
engine, the conditions in the compound are more nearly 
those of non-conducting cylinders, while the ratio of ex- 
pansion is greater, and hence a greater amount of conden- 
sation during expansion might be expected. Therefore, if 
the initial steam is dry in both cases, we would expect to 
find more moisture in the I. p. cylinder of the compound at 
the end of the expansion than in the simple engine. This 
is by no means a complete statement of the case, and is 


78 COMPOUND LOCOMOTIVES. 


only intended to indicate why the presence of considerable 
moisture in the exhaust from a compound locomotive is 
not necessarily evidence of uneconomical working. 

In discussing this subject, Mr. von Borries has written 
substantially as follows: ‘‘Since in compound engines re- 
evaporation is very much lessened—one of the advantages 
of the system—the steam in the cylinders is always more 
moist than usual, and in the large cylinder always con- 
denses to some extent. In order that the water may not 
have an opportunity to re-evaporate, it should be removed. 
This is most readily accomplished by cutting notches about 
2 millimeters (0.08 inch) in width in the cylinder cocks with 
a sharp-edged file ; by this means the cocks are kept suffi- 
ciently open to allow the water to escape.” ‘‘ The steam 
escaping from the stack is always wet; this, however, 
attends the system, and is no sign of priming, but of the 
fact that much heat has been withdrawn and converted 
into work.” 

In some designs of compound locomotives ‘‘safety valves,” 
or, more properly, automatic water valves, are fitted to the 
]. p. cylinder to prevent damage by possible accumulation 
of water. This is, however, good practice for all large 
steam cylinders. 

The above remarks simply emphasize the statement 
already made as to the advisability of carefully lagging the 
cylinders, and of inclosing the receiver in the smoke-box 
in order that the steam delivered to the 1. p. cylinder may 
be as dry as possible. 

ExHAUST NozzLes.—There is a very noticeable difference 
between the exhaust from compound and simple locomotives. 
Asthe averaze expansion in the compound is considerably 
greater than in the simple engine, the final pressure in the 
low-pressure cylinder is comparatively low and the 
intensity of the blast is therefore much reduced. Also, 
instead of four exhausts in rapid succession during a revo- 
lution there are but two, and the total volume of steam 


COMPOUND LOCOMOTIVES. 79 


exhausted in a revolution issomewhat greater. The re- 
sult isa more even and less intense urging of the fire, 
from which more perfect combustion and transfer of heat 
to the boiler are to be expected, while the quantity of 
small coal drawn through the tubes will be proportionally 
less. 

The single circular nozzle appears to be the favorite with 
the designers of compound locomotives abroad, the 
diameter of the nozzle being in the two-cylinder compound 
engines concerning which the writer has information, 
about one-fifth of the diameter of the low-pressure cylin- 
der. The best proportion will naturally have to be deter- 
mined by experience for different kinds of coal and for the 
various kinds of service. 

SEQUENCE OF CRANKS.—The natural sequence of the 
cranks in two-cylinder compound locomotives would seem 
to be to place the low-pressure crank 90 degrees behind the 
high-pressure crank for forward running. Mr. Urquhart 
is reported as having tried the effect of placing the low- 
pressure crank leading in forward motion. The following 
is quoted from a paper recently read by him in England, as 
given by the Master Mechanic: ‘‘From indicator diagrams 
taken in forward gear with the latter arrangement, it ap- 
pears that inconvenient and very excessive compression 
takes place at the first notch in the high-pressure cylinder; 
so much, indeed, that this notch is not used, but in all 
other notches a good distribution takes place. In the low- 
_ pressure cylinder a much better distribution takes place at 
all notches compared with engines having the high- 
pressure crank leading; and this engine with the low- 
pressure crank leading, which has only recently been put 
to work, seems to develop more power and to burn less 
fuel than the others having the high-pressure crank lead- 
ing. . . . The receiver capacity is equal to that of the 
high-pressure cylinder, and all the dimensions are the same 
in both the above cases. The idea of making one engine, by 


80 COMPOUND LOCOMOTIVES. 


way of trial, with the low-pressure crank leading in forward 
running originated in its being’ accidentally noticed that 
one of the other engines, compounded with the high- 
pressure crank leading in forward running, seemed to work 
better and to be more powerful, developing its full tractive 
force with an earlier cut-off and making steam with greater 
freedom, when running backward with its train, in which 
case, of course, the low-pressure crank became the leading 
one. . . . The only objection the author now sees to the 
low-pressure crank leading is that it gives too much power 
in the large cylinder and too little in thesmall, thus putting 
the engine out of equilibrium; but this irregularity will in 
a great measure be obviated by having a receiver about 
half as large again as those now used on all the present 
compounds.” 

The writer has not as yet been able to discover any 
reason why, with a valve gear which gives an approxi- 
mately equal distribution for both ends of the cylinders, 
and with the usual long connecting rods, there should be 
any practical difference in the steam distribution with the 
two arrangements of cranks mentioned. Neglecting for 
the moment the irregularity caused by the connecting rods. 
for any position of the high-pressure crank, the low-press- 
ure is at the same relative point in its revolution whether 
it is leading or following. For example, if the high-press- 
ure crank is at a dead point, the low-pressure crank will be 
at either the upper or the lower half center, and the piston 
and valve will be in the same relative positions, the only 
difference being that the piston is making the forward 
stroke in one case and the backward stroke in the other. 
The same is evidently true for all positions of the high- 
pressure crank, The relative direction of the stroke will 
be changed, but the high-pressure piston will be at the 
same distance from the beginning of a stroke, whether its 
crank is leading or following. The irregularity in steam 
distribution caused by the connecting rods must be slight. 


COMPOUND LOCOMOTIVES. 81 


with the long rods which are commonly used in locomotive 
practice. 

It would seem that there must be some other explana- 
tion of the difference found by Mr. Urquhart than the 
sequence of the cranks, and that the real cause has escaped 
his notice during the short time which this engine, with 
the low-pressure crank leading, has been in operation. 


ORLA TEE Vite 





ECONOMY OF TWo-CYLINDER COMPOUND LOCOMOTIVES, — 
The various reasons why compound locomotives should 
be more economical than those of the common type have 
been so often stated at length before the railway clubs in 
this country, before engineering societies abroad, and by 
the advocates of the different systems of compound loco- 
motive construction, and the whole theory of compound 
or multiple-cylinder engines has been so thoroughly devel- 
oped, especially in the numerous books on the steam en- 
gine, that an extended discussion of the question in this 
chapter seems to be uncalled for. Nor does the compound 
locomotive need the support of arguments to show why it 
should be more economical than locomotives of the or- 
dinary type, inasmuch as the economy of the compound 
has been repeatedly demonstrated by that best of all argu- 
ments, actual tests in service. 

Admitting, then, that a noticeable saving in fuel follows 
the use of compound locomotives, there remains to be 
shown the actual amount of this saving, under what cir- 
cumstances it will pay to build compound locomotives, and 
the conditions which will make it advisable to alter existing 
simple locomotives. 

The accompanying table contains a list of comparative 
tests of compound and simple locomotives which would 
seem to be sufficiently comprehensive in number, duration, 
boiler pressures, location and kind of service to convince 
the most skeptical that there is considerable saving in the 
use of the compound system. The data for this table have 
been collected from various sources which are presumably 
reliable. A considerable number of tests are quoted from 
Mr, Lapage, and for the more recent results in Saxony, I 














COMPARATIVE 
4 
| 

Where Tests 
No. were made. Date. Dur: 
vee es 
1./Prussia.....- 1883 | 2 mo 
ae Sad blac washes 1883 | 2 mo 
a lS Aiea: 1883-4) 9 mo 
4, hh ae 1883-4' § mo 
6. Be we eS 1884 2 mo 
6.) os ‘ 1884 2 mo 
TeNIHOLA Us. Siok TSE IT cies 
8.|Prussia ..... 1884-5| 2 mo 
9, se 1884-5! 2 mo 
10. be, paper reas 1885 | 4 mo 
11. England.... |1886 | 3 mo 
12. ‘ Los ey | { 
132 Prussians... sc 1887 | 6 mo 
14. Saxony.......1887 | 6 mo 
iby VERE 1887 | 4 mo 

Argentine | 
al Republic \ (1887 1 mo 
17. England.,.... 1888 | 2 mo 
18 |Saxony...... 1887-8 18 mo 
19. pa Gere i , 1887-8 18 mo 


























7) 
a | 4 . 
: 9 Cylinders. 
S 
Whore Tet ead ener pa 
ere Tests 
No. were made. Date.| Duration. Hs oa 
‘p ‘ 2o| «8 oo 
E%| “it | Diameter,| <= 
i: Geet Inches. i 
ie 4 2 TL 
eS ee! nae 3 ie 1 esl SS Ga 
a, ‘tae 
az - 
1.'Prussia....... 1883 | 2 months {| ; eaee are eg 
pd foxes se, 
an 1883 | 2 months {|} |-------: SB tts fa 8 
an ieee-dt Ssrionthas be, fentecan| Ae ae O28 
3 4. et he Ni 1883-4, § months { : eet Sa Sopa ane 
4 Qo. OS, 1884 | 2 months { : a aed eter G oe 
a gst 2 months {) fa | OFS | 
iB: = & 2 
Me} 7.\India........ 1884 eee: Rees ag pines ie 
a : | 23 69 
8.'Prussgia .....| siete 2 months { : eee At oR ‘ia oa a5 
bt y) 
1884-5 2 months {| 7777777) "tg 51 "| So'08 
t 10. See 1885 | 4 months : i < af vies ais 3 oe: 
& 11. England.... 1886 | 3 months { te tari a or , uae ee 
Be = 10 | 185,091 |18 26 | 24 
| ae, 1886-7) ....-- seers { AR RN) 1320 aS own, mein Reaeg ake 
4 3.372 |18.11 25.6 | 24.8 
fe 13.’ Prussia...... 1887 | 6 months \ 4 ey 17.79 04.8 
3 | fon 6.77 18.12, 25.6 at 
} il 4,426 16.75 
Pegacany.. «11887 | 6 months 4 | 4 9°91 18 4 
, M2 | 1808 17.25 24.75] 21.6 
Mig |... oP CACTI Ee | a a 
oe, OSS ames 19 Fs Erg eae 3,638 [16 23.25) 24 
16. ATE lie { 1887 | 1 month t | 3937 |..:... Sr Wes 
<a 893 18 26 24 
17. England.....|1888 | 2 months \/""""| gga}... |... | 
. 1 46,206 |16.55 23.6 | 22.1 | 
18 7a mS 1887-8 18 months 1 45,285 16:55 99 1 
f 10 ee ee a of 
1 21,20 16. 
19. | DoS , 1887-8 18 months 4 26,459 18 4 
(12 | 19008) 18 24 


























* Per 100 axle miles. 








Pressure, 


Boiler 
Pounds. 


6.2 2 wig e 2.3 2-8 


132.3) 


Number 


Driving 
W heels. 


e 
Be 


Grate Area, Square 


feet. 
Total Heating Sur- | 


Ooo Ooo | 


Loo LEE PE AIAIODOCOo Gm 


coupled. 


4 


Oo So S3 Oo > 


ete ee eee: | 
| i9? 58 1098.9 


COMPARATIVE FUEL CONSUMPTION OF TWo-CYLINDER COMPOUND AND ORDINARY LOCOMOTIVES. 


nae eel 


Square 


Inches. 
face, 


Diameter, 
feet. 


52.36) 16.47|1308. ‘ 
54.02/18 .30|1259 .4 


52.36/16.47)1308 .9 
51.10/21.53|1345.5 


52 .36|16.47/1308.9 
52.36|16.47|1340 .2 


44.49} 5.81) 247.6 
44.49} 5.81) 247.6 
52..36|10.47|1308.9: 
52 .26|16.47/1340.2 
52.36|16 47/1308 .9 
52.36) 16.47/1340.2 


18.84|1054.9 
1938/1038 .7 
18 .84|1054.9 
16 .68)1334.8 
16.47|1308 9 
16.47)1340.2 


73.23 
73.23 
73.23! 
77.95 
52.36 
52.36 
84 





52.3 |16.68'1291.7 
52.3 |16.68 1345.5 


55.6 (15.17 1238.1 
55.6 '15.17 1288.1 
55 6 15.17 1237.8: 
55.6 15.17 1235.7: 
73.75 


| 





os. me @ | Feese 2 6 eo 
e &% «¢ Bigs o'2 & Ss 
eee ere 

e's. 6.0 @ 1 D6) 6 peas 


61, @°0 © | Sen.e ace ia 


75 
75 19.58 1098.9 
55 6 15.17 1238.1 


“65.6 15-17 72384 


55.6. 15103233 
55.6 15.17 1235.7 


+t Engine and tender. 


af © 2S Viele Sie wee) ©. 2 or Oe 


© CP OL igig ac PED 12 2 2 2 999 








ts lee Wie 
SS 6. 14% 
Mat ft DN a 
Sg eT SS 
on BE may 
te Ao | bo 
aa) oh an Remarks. 
DRO] & o 
od s | &f 
SES] SS 88 
eG = nl 
E O In 
45.4 149 ae Freight. 
40.8 | 59.96*|18 
(Two snecia: trains on 
43.1 | 73.80*| . \f mountain sections 
7.4 | 92. 25% 20 |* only. Max. grade, 1 in 
\ 64. 
(S Saving calculated from 
SRR rene ae average actual con- 
42.4 eri ptt { sumption and ordinary 
' consumption. 
1h Ga eis Poy Local passenger. Saving 
UBS ths ae { as in No 
43.1 | &7.98* Freight 
42.4 | 67.06*|14.3) *§ 
43.1 | 46.48%), - |Special. 
42.7 | 55.35” 16 
33 10 Both types of engines do- 
82 98 1435 ing ee same class of 
wo 
41.9 127.73") ....|Special, passenger. 
38.5 |152.56*|16 sb 
41.9 |115.47*|. Passenger. 
47.9 |170.30*|14.5 
43.1 | 64.58%}. -|Freight. 
42.4 | 76.64*|16 
49.8 | 29.4 |....|/Passenger. 
aks da.8 113 <¢ 
45.2 | 34.9 |..../Freight. 
Seipaiee ELL! RMeG 8 0: Sy # fetes 
9 Coal trains—load drawn 
42.9 | 40.08 by compound 8 per cent. 
a 9 | 47.55 |16_ aie 
45.1 | 43.1 Freight 
44.4 | 56.7 as 
A250 22.0 oe 
43.5 | 55.7 (22.6) < 
| Ce Oh renee eral oat eee et 
ae ot era, 18) Sac eae See ee 
40 22.36 |....|Passenger. 
es 28.19 |20.7 < | 
| 91 1+} 28.3 |....|/Passenger. 
S025 30 O21 e 
47.4 | 25.2 |....|Express, 
46.1 | 31.9 (21 3 
45.8 | 43.4 |..../Freight. 
44.4 | 52.9 |18 a 
42.9 | 522 \i7 tr 
43.5 


bo.2 Aa as 


ene et 


COMPOUND LOCOMOTIVES. 83 


am indebted to Mr. D. L. Barnes. The table shows that 
the saving in fuel is from 13 to 24 per cent., and it will be 
noticed that the highest percentage of saving is for a six 
months’ trial (No. 14) of two engines working with the 
same boiler pressure and of almost identical dimensions. 
Other cases in which the same boiler pressure was used are 
Nos. 2, 4, 6, 7,16and19. In No.7 the boiler pressure was 
but 120 pounds, which is generally admitted to be too low 
for the best results ot compound working. The saving in 
this case was 13.5 per cent., and the next lowest, with 
equal boiler pressure, is(No, 6) 16 per cent, 

It has been claimed by several engineers, whose reputa- 
tions give weight to their opinions, that a large part of the 
economy of compound locomotives is due to the higher 
boiler pressures employed, and that equally good results 
can be obtained with simple engines. On the other hand, 
engineers of equal prominence have failed to find any ma- 
terial advantage in the use of what may to-day be called 
high pressures in ordinary locomotives. There is undoubt- 
edly from theoretical considerations a marked economy in 
the use of high pressures, provided that full advantage is 
taken of the greater range of expansion which the higher 
pressure makes possible. It is not practicable to obtain 
economical results if a large ratio of expansion is used in 
one cylinder, on account of the greater condensation, to say 
nothing of the great variation in the pressure on the crank 
pin during a stroke. We thus find two conditions which 
are conflicting as the pressure is increased, and in the loco- 
motive we have the further obstacle that with the ordinary 
forms of valve gear it is not practicable to cut off steam 
very early in the stroke. There is no advantage in using 
‘higher pressures and correspondingly smaller cylinders, so 
that the points of cut-off will remain about the same as 
with the lower pressure, because while the volume used 
per stroke to obtain the same total pressure on the piston 
is less, the weight of each cubic feot of steam has increased 


84. COMPOUND LOCOMOTIVES. 


with the pressure, and the amount of heat drawn from the 
boiler per stroke will be very nearly the same. 

In the compound or multiple-cylinder engine advantage 
may be taken of the possibilities of high-pressure steam 
without encountering the losses which follow from 
extremely early cut-offs in a single cylinder. This is 
another point of superiority of the compound engine, and 
while some saving may be accomplished in the simple 
locomotive with higher pressure by means of somewhat 
smaller cylinders and a slightly earlier cut-off where 
practicable, it does not appear that a saving of fuel equal 
to that of compound engines can be reasonably expected. 

The general average of the results in the table, computed 
by giving each test a value proportionate to the time 
covered by it, is 18.5 per cent. Making allowance for the 
probability of -special care having been exercised in some 
of these tests in favor of the compound, it would seem to 
be safe to estimate upon the basis of 15 per cent, saving. - 
The annual saving per engine on any road on the basis of 
an assumed percentage, such as 15 per cent., is of course 
easily calculable from the record of engine mileage and 
fuel consumption. If the ordinary engine for which it is 
desired to substitute a compound makes M miles per 
annum and 7’ miles per ton of coal, which costs D dollars 
per ton, the annual saving by the compound would be in 


LLB ONT OKT, 
dollars a For example, with coal at $2 per 





ton, 30 miles per ton, and 20,000 miles per annum, the 
: : 20.000 x 2 xX .15 
annual saving per engine would be =o ee 
= $200. It is obvious that the advisability of using the 
compound system varies directly with the total cost of fuel 
per engine per annum, and not necessarily upon the cost 
of fuel per ton. For instance, with 25 miles per ton, 25,000 
miles per annum, and coal at $1.33 per ton, the annual 
saving per engine will be the same as that given above. 


COMPOUND LOCOMOTIVES. 85 


Mr. von Borries gives the cost of his compound locomo- 
tives in one case as from 2 to 3 per cent., and in an- 
other case 4 per cent., more than ordinary locomotives 
of equal weight. He also states that ‘‘ The power of com- 
pound freight locomotives is known by experiment to be 
Sto 10 per cent. and of compound passenger and ex- 
press locomotives 10 to 15 per cent. higher than that 
of ordinary locomotives of equal weight, so far as not 
hindered by the adhesion of drivers to rails. For an equal 
power the compound passenger locomotive is lighter and 
cheaper than the ordinary locomotive.” Accordingly, for 
equal powers, the first cost is ‘‘ in freight engines two to five 
per cent., andin passenger engines eight to twelve per 
cent. lower than ordinary locomotives, similar construction 
of course being assumed in both cases.” Mr. Lapage makes 
a similar argument in comparing a compound with 
a simple engine weighing about 364 tons full. ‘‘ As 
there is a saving of from 144 to 20 per cent. of 
fuel, the grate area and heating surface may be 
reduced in proportion, and also the boiler slightly; 
and the boiler not being so large will bear a 
somewhat higher pressure, while the weight of water 
in it will also be less. These items make a consider- 
able difference, for the boiler alone weighs about 8.75 tons, 
and the water it contains about 2.4 tons, making a total 
weight of 11.15 tons, of which about 1.5 tons may be saved 
with the compound. Again, the motion work, springs 
etc., may be made somewhat lighter, as the strain on the 
compound is not so great as on the ordinary engine. With- 
out taking this into consideration, however, there is a sav- 
ing in metal of about .75 ton in the boiler alone.” The 
‘saving in the weight of the tender, as less fuel and water 
‘are required for the same service, is estimated at about two 
tons, thus making the saving of metalin the engine and 
tender about three tons. ‘‘ The cost of the compound for the 
same power is thus brought to about the same as that 


86 COMPOUND LOCOMOTIVES. 


of the ordinary engine, or rather less, The engine and 
tender being lighter and requiring less coal and-water, 
there is a consequent saving in the hauling.” 

These conclusions are logical, but it does not follow that 
it will be considered advisable in many cases to reduce the 
capacity and consequently the weight of the tender, as the 
increased endurance of the engine with the present tank 
and coal space may be of more importance. However, the 
subject of the most economical capacity of tenders for a 
particular line of service has not in many cases received 
the attention to which its importance entitles it. On the ° 
assumption that the proportions of the boiler of the simple 
engine which is to be replaced by a compound are satisfac- 
tory, including grate and heating surface and steam space, 
there is a possible reduction in these which is worthy of 
consideration. To offset this we will have the increased 
weight of cylinders, pipes, etc., in the smoke-box, and or- 
dinarily some increase in the thickness of boiler plates fol- 
lowing the increased pressures, In view of the lack of ex- 
perimental data of compound locomotives in this country 
at the present time, it would seem to be advisable to disre- 
gard these possible reductions in first cost. 

The figures given by Mr. von Borries, from two to four 
per cent. more than the cost of ordinary locomotives of equal 
weight, or, on the above basis, for the same work, are pre- 
sumably based upon the cost of a number of engines, and 
would not therefore be sufficient for a single engtne if the 
cost of drawings and other expenses incident to getting out 
a new design are to be charged to it. But even if all ex- 
penses which are properly chargeable to the engine are in- 
cluded, itis apparent that the probable saving of 15 per 
cent. will secure a good return from the investment. It is 
claimed by the advocates of some of the various systems 
of compound locomotives that the cost of their mainte- 
nance is no greater than that of the ordinary engines. 
This claim appears to be reasonable, as the slight increase 


COMPOUND LOCOMOTIVES. 87 


in the cost of repairs which would naturally follow the in- 
troduction of additional parts may be balanced by the in- 
creased endurance of the boiler, taken all together, on ac- 
count of the diminished intensity and frequency of the ex- 
haust. 

The cost of converting simple locomotives to compound 
will depend largely upon the type which the working con- 
ditions make it advisable to adopt. The simplest case will 
be that in which one cylinder of the ordinary engine can 
be retained for the high-pressure cylinder of the compound, 
andasimpie form of starting gear such as Lindner’s is 
adopted. The minimum changes required will then be a 
new cylinder and piston for the low-pressure, new pipes 
for the receiver, etc., a starting valve and connections, a 
safety valve on the receiver, and probably two new slide 
valves and slight changes in the valve motions. The other 
extreme is apparently that in which two new cylinders are 
necessary, and starting and intercepting valves of the 
Mallet type are adopted. In any case the probable cost 
can be closely estimated from a detailed cost sheet of ordi- 
nary engines of similar dimensions in the shops in which 
the alteration is to be made. Mr. Hughes gave the cost of 
converting a 16 X 24 engine in India, which has been 
already referred to, as about two hundred dollars, which 
is probably considerably lower than the same work could 
beedone for in this country. Judging from such cost sheets 
as are at hand, it seems probable that the minimum cost 
would not be less than three hundred dollars, and may be 
as high as seven hundred dollars for the more complicated 
arrangements. But, even with the latter amount as a 
basis, it is evident that there are many cases in which the 
expenditure would be advisable. 


CHAPTER VII. 





THREE-CYLINDER COMPOUND LOCOMOTIVES. 

The first question which naturally arises in beginning the 
consideration of three-cylinder compound locomotives is, 
what are the reasons why that form should be selected in 
any case in preference to the two-cylinder type,. which is 
evidently so much more simple? In answer to this, it may 
be said that the expansion of steam can be carried further 
in some designs of three-cylinder engines"than in the two- 
cylinder type without using cylinders which are excessively 
_ large, and, therefore, that the advantages of high-pressure 
steam can bemore fully realized. The ratio of the volume 
of the low-pressure cylinders to the high-pressure can be 
made greater than is practicable with two cylinders, and a 
more nearly equal distribution of work can, therefore, be 
obtained. By a. proper arrangement of cranks a more 
uniform rotative power can bessecured, and further, a bet- 
ter distribution of weights can be obtained than is possible 
with the two-cylinder outside connected type. 

To avoid possible misunderstanding, attention is called 
to the distinction between three-cylinder compound en- 
gines and triple expansion engines. Inthe latter the steam 
performs work in three cylinders in succession, the high- 
pressure, the intermediate, and the low-pressure. In the 
former, when released from one high-pressure cylinder 
the steam is divided between two low-pressure cylinders, 
or else the exhausts from two high-pressure cylinders unite 
in the receiver and further expansion takes place in one 
low-pressure cylinder. In general the name compound is 
given to those engines in which the steam acts in but two 
cylinders in succession, whether two, three or four cylin- 
ders are used, while triple and quadruple expansion mean 


COMPOUND LOCOMOTIVES. 89 


that the steam is used in three or four cylinders in succes- 
sion. 

The two possible arrangements of three-cylinder com- 
pound engines have been applied to locomotives ; that 
with one high-pressure and two low-pressure cylinders by 
the Northern Railway of France, while that with two high- 
pressure cylinders and one low-pressure is the arrangement 
of the well-known Webb compound. 

Steam Distribution in Three-Cylinder Compound Loco- 
motives.—The fundamental theory of three-cylinder com- 
pound engines does not, of course, differ from that of two- 
cylinder compound engines. The only differences which 
exist are the result of the relative angies of the cranks, and 
are to be found in the variations in the turning moments 
and in the variations in pressures in the receiver. Each 
case must be individually analyzed, and the only difference 
between such analyses and those already given for two- 
cylinder engines is the greater complication which arises 
from having three cranks to consider instead of two. As 
an example of the method to be preferably followed in at- 
tempting such an investigation, an arrangement of cranks 
which has been used for a locomotive is selected. In this 
form the low-pressure cranks are at right angles and the 
high-pressure crank makes angles of 185 degrees with them. 
In the first place we assume the following data: In the high- 
pressure cylinder, cut-off, .75; release, .90; compression, 
-90; in the low-pressure cylinders the same distribution. 

In Fig. 29 are shown successive positions of the three 
cranks, h representing the high-pressure crank, L one low- 
pressure crank, and 7 the other. Assuming the direction 
of the revolution to be as indicated by the arrow, an ex- 
haust takes place from the high-pressure cylinder when its 
crank is ath,. One low-pressure crank, 7,, is then just 
commencing a stroke, and the other, Z,, has accomplished 
about .57 of a stroke, the effect of the angularity of the 
connecting rods being neglected. From these positions 


90 COMPOUND LOCOMOTIVES, 


there is free communication between the three cylinders 
and the receiver until Z moves to L,, where the cut-off 
takes place in that cylinder, the other low-pressure crank 





Fig, 30 


being then at 7, and the high-pressure crank ath,. From 
these positions’ expansion continues in tke cylinder J, 
while there is still freecommunication between the other 


COMPOUND LOCOMOTIVES. 91 


low-pressure cylinder, the receiver and the high-pressure 
cylinder until the low-pressure crank L arrives at L,_, 
when steam is again admitted to that cylinder for the re- 





Fig. 32 


turn stroke. The other low-pressure crank is then at 7,, 
and the _ high-pressure crank is at h,. All three 
cylinders are now again in communication, and remain 


92 COMPOUND LOCOMOTIVES. 


so until the cut-off position 7, is reached, the other cranks 
then being at L,andh,. ‘The two cylinders which are 
represented by A and Z remain in communication until 
the positions numbered ,; are reached, when steam is again 
admitted to the cylinder/. Soon after this the high-press- 
ure exhaust takes place at h,, and a fresh supply of steam 
is admitted to the receiver, from which it enters both low- 
pressure cylinders whose cranks are at L,and7l,. These 
positions correspond to those numbered ,, the direction of 
the piston movement only being changed. It is clear that, 
when the exhaust takes place from the high-pressure cyl- 
inder, the low-pressure piston corresponding to / is always 
near the beginning of a stroke, while the other is near the 
middle of its stroke. The effects of this distribution in the 
low-pressure cylinders are shown in Fig. 30 by indicator 
cards, which are constructed on the assumption of rapid 
valve movements and neglecting the irregularities which 
are caused by the connecting rods. The cards are not 
drawn to a scale and the variations in pressures are pur- 
posely exaggerated. Witha relatively large receiver the 
drop in pressure at /, and L, will be very small. In prac- 
tice the readmission at , would produce a hump in the 
card L, while the card? would have a form which would 
apparently indicate that the valve was late in opening. 

At earlier points of cut-off somewhat different results 
will be found. These are illustrated by Figs. 31 and 82, in 
which it is assumed that cut-off takes place at .4 and re- 
lease at .75 of the stroke in all three cylinders, Taking the 
direction of revolution as before, when release occurs in 
the high-pressure cylinder at h,, one low-pressure crank is 
at L, and the other is at 7,. A very slight movement 
brings the crank Z to its cut-off position Z,, soon after which 
steam is admitted to the other low-pressure cylinder at 1,, 
and that cylinder isin communication with the receiver 
and the high-pressure cylinder until its cut-off point is 
reached atl,. There will then be slight compression in the 


SOMPOUND LOCOMOTIVES. 93 


high-pressure cylinder and the receiver until steam is ad- 
mitted to the L cylinder at the beginning of its next stroke. 
The remaining events of the revolution are similar to those 
already noticed and will be made clear by a study of Fig. 
31. It will be seen that there is still readmission to the 
low-pressure cylinder LZ, but that this does not affect the 
form of the card from the other low-pressure cylinder. 
With this arrangement of cranks and with the same valve 
adjustment the indicator cards from the two low-pressure 
cylinders will be unlike for all points of cut-off. There is 
in fact but one arrangement of cranks for which the dis- 
tribution in the low-pressure cylinders will bethe same, and 
that is when the low-pressure cranks are both at right 
angles with the high-pressure, and therefore either directly 
opposite each other or parallel. Assuming an equal di- 
vision of work between the three cylinders, the most uni- 
form turning moment will be obtained by placing the 
cranks at angles of 120 degrees with each other, but the 
difference in the distribution in the two low-pressure 
cylinders will still exist, although it is not probable that 
this will be of great importance at ordinary running 
speeds. 

An examination of the crank positions for the form of 
three-cylinder engine having two high-pressure cylinders 
and one low-pressure cylinder shows similar peculiarities 
in the distribution. This will be evident from Figs. 33 and 
34, which are lettered similarly to Figs. 29 and 31, Hand h 
representing the two high-pressure cranks, which are at 
right angles, and 7 the low-pressure crank, which makes 
angles of 135 degrees with the others, The distribution in 
Fig. 33 is the same as that in Fig. 29, and that in Fig. 34 is 
the same as that in Fig. 31. It will be seen that there is 
readmission to the low-pressure cylinder in both figures; 
but at the earlier cut-off of four-tenths it is not probable 
that the effect on a low-pressure indicator card would be 
noticeable. Placing the cranks at angles of 120 degrees 


94 COMPOUND LOCOMOTIVES. 


would, as in the first arrangement of cylinders, produce 
very little change in the indicator cards. 

It is evident, from the preceding partial analysis of the 
steam distribution, that the construction of theoretical indi- 
cator cards for three-cylinder compound engines will be 
considerably more difficult than for the two-cylinder type, 
but that the same formulas and methods of construction 





Fig. 34 


can be used. The remarks which were made in discussing 
two-cylinder compound locomotives in regard to the effect 
of varying the capacity of the receiver and the results of 
changing the points of cut-off are equally applicable to 
three-cylinder engines. In fact, the only differences are 
those in the steam distribution, which have been already 
discussed, and which depend upon the angles made by the 
three cranks. 

A mathematical discussion of the three-cylinder type of 
compound engine, having one high-pressure cylinder and 
two low-pressure cylinders, and with the cranks placed at 
angles of 120 degrees with each other, will be found in the 
appendix to ‘‘ The Marine Steam Engine,” by R. Sennett. 
The form having two high-pressure cylinders and one low- 
pressure cylinder does not appear to have been used in 


COMPOUND LOCOMOTIVES. 95 


marine practice, and its use is not to be expected, inas- 
much as one of the chief reasons for using three cylinders 
instead of two is to avoid excessively large low-pressure 
cylinders. 

In attempting to determine the size of cylinders for 
three-cylinder compound locomotives, the best guide will 
undoubtedly be the results obtained with locomotives of 
that form in practice. When such information is not 
obtainable, the most satisfactory method will be that 
advocated under similar circumstances for two-cylinder 
compound engines, 7. e., the construction of, what were 
called for convenience, theoretical indicator cards, and the 
alteration of these as experience dictates, to allow for 
wire-drawing during the opening and closing of valves, 
drop in pressure, etc. The proportions which appear to 
have been generally adopted by Mr. Webb are, high- 
pressure cylinders, 14 inches in diameter; low-pressure 
cylinder 80 inches in diameter; stroke of all pistons, 
24 inches. The ratio of the volume of the low- 
pressure cylinder to that of both high-pressure cylinders is 
thus about 2.3. Assuming a mean forward pressure of 
175 pounds gauge, in the high-pressure cylinders, 
and a back pressure in the low-pressure cylinder 
of 3 pounds above the atmospheric pressure 
and an equal division of work, we can make an 
approximate estimate of the maximum power of the 
engine as follows: The area of the low-pressure piston is 
4.6 times that of one high-pressure piston, and, if the work 
is to be the same in both, the mean pressure in a high- 
pressure cylinder must be 4.6 times that in the low-pressure 
cylinder. As the total range of pressure is 172 pounds, 
and as the mean receiver pressure is approximately the 
same as the mean high-pressure back pressure and the 
mean low-pressure forward pressure, we have: 4.6 x l. p. 
mean effective pressure = 172—1. p. mean effective, whence 
1, p. mean effective = 172 + 5.6 = 30.7 pounds. The mean 


96 * COMPOUND LOCOMOTIVES. 


receiver pressure is then 30.7 + 3 = 33.7 by gauge, and the 
mean effective in the high-pressure cylinders is 175 — 338.7 
. =141.38 pounds. A similar calculation can, of course, 
be made with any assumed mean forward pressure, and 
this method can also be used for making an approximate 
comparison of the maximum work done in the cylinders of 
the three-cylinder compound with that in ordinary loco- 
motives. For example, if the mean forward pressure in 
the latter is 150 pounds and the back pressure is 3 pounds 
as before, the total effective pressure during a stroke will 
be 2 x 147 x area of one piston. To be the equivalent of 
the compound locomotive this must equal 3 x 141.3 x area 
of one high-pressure piston. This gives in the present case 
221.9 square inches as the piston area of the simple engine, 
or in other words a simple engine having two cylinders 
about 16.8 inches in diameter would be equal in power, 
with the assumed pressures, to the compound engine 
having cylinders 14, 14 and 380 inches in diameter, the 
stroke being the same in all cylinders. 

The same method can be used to find dimensions for an 
equivalent three-cylinder engine having one high-pressure 
and two low-pressure cylinders. If the ratio of the volumes 
of the two low-pressure cylinders to that of the high- 
pressure cylinder is 2.3, each low-pressure cylinder will be 
1.15 times as large as the high-pressure. Therefore 1.15 X 
1, p. mean effective pressure = 172 — 1. p. mean effective, 
whence 1. p. mean effective = 80 pounds. The mean re- 
ceiver pressure will be 83 pounds gauge, and the h. p. 
mean effective pressure will be 175 — 83 = 92 pounds. To 
find the piston areas we have 92 x area of the high-press- 
ure piston for this engine = 141.3 X area of a 14-inch 
cylinder, which gives an area of 236.3 square inches, 17.35 
diameter, for the high-pressure piston, and 1.15 times this 
or 271.8 square inches, 18.6 diameter, for each low-pre sure 
piston. An engine having one high-pressure cylinder 17.35 
inches in diameter and two low-pressure cylinders 18.6 


COMPOUND LOCOMOTIVES. 97 


inches in diameter, is thus equivalent with the assumed 
pressures toone having two high-pressure cylinders 14 
inches in diameter and one low-pressure’ cylinder 30 
inches in diameter. The distribution of work among the 
three cylinders will be considered in a subsequent chapter. 

ILLUSTRATIONS OF THREE-CYLINDER COMPOUND LOcOMo- 
TIVES. —Before discussing other special features of three- 
cylinder compound locomotives, illustrations of the two 
forms will be given. The compound locomotive having 





Fig. 35 


ene high-pressure cylinder and two low-pressure cylinders, 

which was built by the Northern Railway of France, and 

to which reference has already been made, was illustrated 

in Engineering of Dec. 6, 1889. The general arrangement 

of the cylinders and steam connections of this locomotive 
7 


98 COMPOUND LOCOMOTIVES. 


is shown in Fig. 35. Referring to this figure, his the high- 
pressure cylinder; 7,7 are the low-pressure cylinders; A is 
main steam pipe to the high-pressure cylinder; C, C is the 
receiver; and D, Dare the low-pressure exhaust pipes. The 
low-pressure cylinders are placed as usual and have the 
valve chests above. The high-pressure cylinder is placed 
below the smoke-box with its valve chest B below it, and 
is inclined at an angle of one inten. The locomotive is of 
the Mogul type, having six coupled driving wheels, the 
middle axle being the main driving axle for all three cylin- 
ders. The low-pressure cranks are at right angles, and the 
high-pressure crank is midway between them, thus making 
an angle of 135 degrees with each low-pressure crank. It 
will be noticed that the receiver is formed in the cylinder 
castings, and not by pipes, as in the- locomotives previously 
illustrated. The high-pressure valves are a special feature 
of this engine. These consist of a main valve and 
a cut-off valve, which slides on the back of or 
below the main valve, the whole forming a combination 
which in principle is the same as the Meyer and Ryder cut- 
offs. The edges of the cut-off valve form an oblique angle 
with the axis of the cylinder, as in the Ryder valve gear, 
and the ports in the main valve are correspondingly in- 
clined at the back of that valve, but are twisted so that on 
the face next to the cylinder they are placed as is custom- 
ary. The edges of the exhaust port in the cylinder casting 
are, however, inclined, and the exhaust cavity in the main 
valve is formed to correspond. The yoke which drives the 
main valve does not fit it at the sides, and so permits a 
transverse movement while controlling it longitudinally. 
A second yoke incloses the valve, and permits a longitudinal 
movement, but holds it transversely. This yoke is con- 
nected to a stem, which passes through a stuffing-box in the 
side of the valve chest, and is operated from the cab by 
lever connections. It is clear that the high-pressure cut-off 
can be adjusted at any time by means of this connection, 


COMPOUND LOCOMOTIVES. 99 


while the valve is so proportioned that in its extreme posi- 
tion the steam and exhaust ports remain open for all posi- 
tions of the high-pressure piston, and steam is thus allowed 
‘to blow through the high-pressure cylinder without doing 
work. The engine can, therefore, be started by the low- 
pressure cylinders with steam from the boiler, the high- 
pressure piston being then practically inoperative; and as 
‘the low-pressure cranks are at right angles, the starting 
‘conditions will be the same as for a simple locomotive. The 
principal dimensions of this locomotive are as follows : 


‘Diameter of high-pressure cylinder (original). ..... 18.11 inches. 

66 (present)....... 17 ne 

‘7 ** low-pressure cylinders (2)........ .... 19.69 <* 
Re MRMOR GL DISLONE. be) sas cuivesae case senses .508s rea ct ee Ma 
‘Diameter of driving wheels............ eH eip Bee Gl Sirk y £8 
MOM CTS PLOASUTO; LAM LE ees cc cineaebetesessenvceccccce 199 pounds. 
‘Diameter of boiler, smallest inside............. ... 52.3 inches. 
Pintbos 208, 1.17 inches, lOng@th. Jace cccocs dense ceesses 13 ft. 1.48 inches. 
ONES oc hapwaipartadwesveaas's PRL a titarn ee dees 22.5 sq. ft. 
PORE OISUT TAGE 5 Hat ota. sein ehpre neat a wramm ca Ceres eb esas 1224,9. <° 
‘Weight in working order, ROUAL AEE Se alte a eens 106,176 pounds. 

on driving wheels...... 90, 944 

LOw-pressure Valve Gear........sseee o---- cess Walschaert. 
Exhaust nozzle, 4.21 inches in diameter, originally 5.51 inches. 


The general arrangement of the cylinders and steam 
connections of compound locomotives of the Webb system 
is illustrated by Fig. 36. In this figure h, h are the high- 
pressure cylinders, which are placed so that the centers are 
in a transverse line about four feet back of the front tube 
sheet, and which are connected to the second pair of 
Griving wheels. The low-pressure cylinder / is placed be- 
neath the smoke box and is connected to the forward pair 
of driving wheels. The course of' the steam from the 
boiler is through the pipes A, A to B, B, and thence back 
to the high-pressure cylinders. The exhaust from 
these cylinders is led through the pipes D, D, and 
thence around the smoke box through two pipes C 
to the low-pressure steam chest. The course of the 
exhaust from the low-pressure cylinder is clearly in- 
dicated in the figure. The disposition of the cylinders and 


100 COMPOUND LOCOMOTIVES. 


steam pipes is essentially the same in the Webb compounds 
for passenger and freight service. The most noticeable 
peculiarity of the system is the absence of driving connec- 
tion between the high and low pressure axles, there being 





Fig. 36 


no coupling rods on engines having two pairs of driving 
wheels. In one design for freight service there are three 
driving axles, the first Leing driven by the low-pressure 
cylinder, and the second and third, which are coupled, be- 
ing driven by the high-pressure cylinders. It will be seen 


COMPOUND LOCOMOTIVES. 101 


that even in this case there is no connection by coupling 
rods between the high and low pressure cylinders. The 
principal dimensions of a recent Webb compound locomo- 
tive are as follows: 


Diameter of high-pressure cylinders (2).............. 14 inches. 
- low-pressure Cylinder.......-.sscecs-eee SOLR SSG 
Stroke Of all pistons.............secccccecsccsccccccese 24 «ff 
Diameter of driving wheels (4).......cccscsescccccces ESD 
eee PIPOCURUITO, PAUSE. 6.5 ccs teccacecn shesesupeseese 175 pounds. 
Diameter of boiler, gin llest MBG sss as cst ek sce 49 inches. 
Tubes, 235, 1% in., length ........... Mest eisiatee #1 naie' bs ae 11 ft. 3in. 
MTN eho Sk wala oa cee vep av ua teas eae ee Waste awgawesede eae 55 sq. ft. 
MEMO PANE MUTI CE... sass cesta de spincindeenecvaensnc scsi 1456.7 ‘* 
Weight i in working GIaers LOtAle tect cee oe tween ee 99,350 pounds. 
on driving wheels........ 66,700 


MIEPs)! oa 5252 = od chk ok Sete stint Sisve Ga Peeewes'e res Joy 
ETE EG OZZIO. co cdcde'cden cvs ckeencdanvees esetnscedsee-454 10. in diam, 


OT ASE aay Gti 





DISTRIBUTION OF WORK IN THREE-CYLINDER COMPOUND 
LOCOMOTIVES.—It was shown in the theoretical discussion 
of the distribution of work between the cylinders-of two- 
cylinder receiver compound locomotives, that with the 
same points of cut-off in both cylinders and with the ratios 
of cylinder volumes which are practicable in locomotives, 
considerably more than one-half of the total work will be: 
done by the low-pressure cylinder. It was also demon- 
strated that the work can be to a great extent equalized 
by making the cut-off in the high-pressure. earlier than eae 
in the low-pressure cylinder. 

The same process of reasoning can be applied to the threes 
cylinder type of compound engines, inasmuch as we may 
regard this form as a development of the two-cylinder 
type, produced by substituting either two smaller high- 
pressure cylinders for the original high-pressure cylinder, 
or else two smaller low-pressure cylinders for the original 
single low-pressure cylinder. It is, therefore, to be ex- 
pected that, with the same points of cut-off in all three 
cylinders, considerably more than one-half of the total 
work will be done in the single low-pressure cylinder of the 
Webb type of compound locomotive, and in the two low- 
pressure cylinders of the other form of three-cylinder com- 
pound locomotive which, for the sake of brevity, may be 
called the French type. We may even go a step further 
and say that, with the ratios of cylinder volumes which 
are practicable, the total work cannot be so divided that 
much less than one-half of it will be done in the low-press- 
ure cylinders. This statement is borne out by the pub- 
lished indicator cards of the Webb locomotive and leads to 
some interesting conclusions. 


COMPOUND LOCOMOTIVES. 103. 


These indicator cards show that the proportion of the 
total work which is done in the low-pressure cylinder is 
from 50 to 65 per cent. at various speeds, with the low- 
pressure valve in full gear. As making the low-pressure 
cut-off earlier would increase the proportion of work done 
in that cylinder, it follows directly that the low-pressure 
cylinder’s share of the total work is at least 50 per cent. 
As the Webb locomotive has no coupling rods between the 
high and low-pressure axles, and as the weight on each 
pair of -drivers is very nearly the same, it is evident that 
this division of work is the best under the circumstances. 
This point and others can be well illustrated by a diagram 









A 
+ a ST 
S 






{ res 
i ! | 
"I maeN 
| Cal as | 2 Lo Ler NE 
_ . ! aa was eA oy a ea ~ 
} Pie 3 ‘hi 19 eas | eet Lay: 
Se peek he ie ane AON TE bt 
| Wate. fl { , | | Ny Al i x | H 
| ee. L/ H Ve | | | 3% SY Y fond | \y <I | | 
A stip H | i H H “4 \ re | f ele ! 
a g k 


Fig. 37 


of crank efforts. Such a diagram is shown by Fig. 37, 
which was constructed from indicator cards of a Webb 
locomotive which were published in Engineering, May 24, 
1889. Steam was cut off at about ten inches in the high- 
pressure cylinders, and the low-pressure admission was at 
*‘full gear.” The speed is not recorded, but from the form 
of the high-pressure admission line is evidently not great. 
The mean pressure is approximately 81 pounds in the high- 
pressure cylinders, and about 34 pounds in the low-pressure 
cylinder, which is equivalent to 34 X 2.3 = 78.2 pounds in. 
the two high-pressure cylinders, the work done in the low- 
pressure cylinder thus being nearly one-half of the total. 


104 COMPOUND LOCOMOTIVES. 


Referring to Fig 37,a bedeandf g hk 1 show the vari- 
ations in the turning moments, or the tangential efforts on 
the cranks, of the two high-pressure pistons, the cranks 
being at right angles, and the irregularity caused by the 
connecting rods being neglected. The combined efforts on 
these two cranks is shown by the curve f p ql. The 
variations in the turning moments on the low-pressure 
crank are shown by a curve such as BC D, and if we 
assume that the low-pressure crank makes angles of 135 
degrees with the high-pressure cranks, this curve and that 
for the other stroke D E F A B will be located as shown in 
the figure. Combining the high and low pressure diagrams 
gives the full line curve in the figure which represents the 
variations in the pulling power of the locomotive during 
one revolution, as shown by the indicator cards, and there- 
fore without taking the inertia of moving parts into con- 
sideration. A comparison of this full line curve with the 
curve of the combined high-pressure cylinders f p g 1 shows 
that the angles between the low-pressure and the two high- 
pressure cranks are not of great importance. If the low- 
pressure crank were moved back about 25 degrees, so that 
the maximum moment for the low-pressure crank at C 
would coincide with the minimum for the combined high- 
pressure cranks at p, the combined diagram for all three 
cranks would be somewhat more uniform, but the differ- 
ence would not be great. A diagram of crank efforts on 
the assumption of uniform steam pressures throughout the 
stroke in each cylinder shows similar peculiarities. 

It would seem to be evident from this partial investiga- 
tion that there would be very little advantage in connect- 
ing the high and low-pressure axles of this type of locomo- 
tive by coupling rods, excepting possibly for starting, and 
that, if the suppression of coupling rods is an object of im- 
portance, Mr. Webb’s design meets the requirement as 
well as possible with three cylinders. It has been sug- 
gested that this type of locomotive might be improved by 


COMPOUND LOCOMOTIVES. 105 


placing the cranks at angles of 120 degrees and coupling 
- the driving wheels. The effect of this, with the steam 
distribution and division of work used in the construction 
of Fig. 37, is shown by Fig. 38, in which the full line curve 
shows the variations in the combined rotative efforts on 
the three cranks. It will be seen that the minimum turn- 
ing moment is greater than that in Fig. 37 and the maxi- 
mum is less. so that there is a more uniform effort through- 
out the revolution. The performance of the locomotive at 
slow speeds would therefore be improved by this arrange- 
ment, but as the speed is increased the inertia of the moy- 
ing parts tends to diminish this apparent advantage, so that 







; | 
| 
> ia | : ol ea 
ee | bert 
ah Be a Va a ee ae | Lea AS en 
se ff EN AOR 4 eee ae ves 
Be tet EO PAA 

TN oc= an 

! { \/ H ou \ rs | | 7 Ns 4 ae | 
pee A ined Eee Ee CGN SS on Bs 
a he fit A hoch RT EN 
Ps,0 Lege ey SR Sh a Rd ga Py te 
a oe bet Ce ead Ue UAL Bee ee 








Fig. 38 
it is doubtful if there would then be any practical gain by 
the introduction of coupling-rods. 

Turning now to the French type of three-cylinder com- 
pound locomotives, it will be found that an application of 
the same method of reasoning leads to very different re- 
sults. As has been pointed out, the steam distribution is 
different in the two low-pressure cylinders, but it is never- 
theless to be expected that more than one-half of the total 
work will be done in the low-pressure cylinders with the 
same points of cut-off in all three cylinders. Also by ad- 
justing the points of cut-off, the proportion of the total 
work done in the high-pressure cylinder can be decreased. 
It is therefore possible with this type of engine to divide 
the total work equally among the three cylinders. 


A diagram of crank efforts 


COMPOUND LOCOMOTIVES. 
In this locomotive the two low-pressure cranks are placed 
with this crank arrangement and on the basis of an equal 


at rizht angles, and the high-pressure crank is placed at 


135 degrees with the otbers. 


106 





a fas UJ 
ee Ry oe one Bee Roy aes pert 
/ , / Fa 
Ne ee 9 qt a0 | ee ey ee A. 
Xx o, ~~ a a 3 
{- nN “ Ss od & i a eras ee om \ —-f-—~-- 
Sea ose Saxe Oe arae 
we & eae q x ; 
sme mete os K---- = Q Se sees rar oak em 
rel \ *. ee iS o { Noo teks 
SS ) Yok oe ee a oN Pens 
oo aa caer be Bis 8 t meee 
\ ere 2B mee Lacie les De ae sree as 
Pras ae Sa 4 
Vet eS f= TEN 
xe ato eee (a) ° fy n ta Ea asrarcae dete Vee ve , 
Ps is os = z bs VW 
/ ‘ Ps MD Pr 7) ah S 
Ree Meili op pep fete fet wpe SE are eg pre ao 
i Page a6 g Bp wes a 
oj 7g . ia] ‘ ’. 
fe, ahi nt eel a ty” oe . a Lx =| E Sloe. >} SSS —s== a" vegit cas eominmeae 
eae Maer air yh 8 some / . 4 
\y ae ° (e) So ‘, ¢ 
sien RRS A AN NAGY ey Mena SW 
[aes Mga s 1S 
i eee OTN Damien ee a ke ae 
Bert erase a" a ee Aa eS 
Vv. wa Wo 5, A A i 1 ed Bae ie 
Sehr at oe qe Be jmeoes 
t s t Ss re 
iN Ne hog ite <a of Rieaaeoaee os se oe 
= ee ee = id “@ RS} a Tan 
\ Se eG od do wars N 
= es Eee \< se (er) o ee ee ae 
, bBGod Y/ 
\ pian Par \ 
re = a) of 
Ro ener Wie pal ENS > maT aby af ee #—-*%-->3 == 
san 9 On 1 at Sa 
/ NS Gis dn ee eg. x a 
aide eee SoHo s GEL 
yes. eee We \ 
Sarg, S ea Ipc gem A 5 apo & PTR ee 
3oODs0 


Fig. 40 
is shown by the full-line curve. 


gram for all three cranks 
If the cranks were placed at angles of 120 degrees, the 


combined diagram would have the form shown by the full- 
line curve in Fig. 40, from which it is clear that this dis- 
position of cranks would give a very constant turning 


moment. 


COMPOUND LOCOMOTIVES. 107 


It follows from these diagrams of crank efforts, in con- 
nection with the previous statements regarding the 
division of the total work, that coupling rods are as much 
a necessity for the French arrangement of cylinders as 
they are a useless complication in the Webb system. The 
work cannot be so divided that as much as one-half of the 
total will be done in the single high-pressure cylinder of 
the former, while nearly one-half is necessarily done in 
the single low-pressure cylinder of the latter. 

STARTING POWER OF THREE-CYLINDER COMPOUND 
LOcOMOTIVES.—It has been already stated that the starting 
conditions for the French type of three-cylinder compound 
locomotive are the same as for an ordinary locomotive, 
inasmuch as the low-pressure cranks are at right angles, 
and the form of valve gear adopted for the high-pressure 
cylinder makes it possible to let steam blow through that 
cylinder without doing work. It is, therefore, possible to 
admit steam at nearly boiler pressure to the low-pressure 
cylinders, and the starting power of the locomotive would 
then be about the same as that of an ordinary locomotive 
having cylinders of the same size as the low-pressure 
cylinders, 19.69 x 27.56 inches, and 199 pounds boiler 
pressure. But as it is not probable that a valve gear of 
that form would be adopted in American practice, it may 
not be out of place to consider the effect of some other 
possible arrangeinent. 

There would not apparently be any practical difficulty 
in the application of starting gear of the Lindner or the 
von Borries-Worsdell type to three-cylinder locomotives of 
thisform. With the Lindner starting gear, steam at re- 
duced pressure is admitted to the receiver, and therefore 
acts as forward pressure on the low-pressure pistons and 
as back pressure on the high-pressure piston. With an ar- 
rangement of cranks such as that of the French locomo- 
tive, this amounts to having an ordinary locomotive with 
19.69 x 27.56 inch cylinders and witha pressure in the 


108 COMPOUND LOCOMOTIVES. 


cylinders equal to about one-half the boiler pressure, aided 
by a single cylinder, 17 inches in diameter, with about the 
same effective pressure. The position of the cranks, for 
which the combined turning moment will apparently have 
its minimum value, is that at which one low-pressure pis- 
ton has passed just beyond the point of latest cut-off. The 
high-pressure crank has then moved through but a small 
angle from a dead point and the other low-pressure crank 
is not far from the half-stroke position. An approximate 
calculation, which is sufficient for our present purpose, 
shows that the combined effort on the crank pins is then 
equal to that of an ordinary locomotive having 19 x 24 
cylinders, at its most disadvantageous position for starting, 
with 174 pounds effective pressure in the cylinders. As 
the weights and diameter of driving wheels of the French 
locomotive do not differ much from those of well-designed 
six-coupled American locomotives having 19 X 24 cylin- 
ders, it is evident that the compound locomotive with the 
simple Lindner starting gear would be fully equal in start- 
ing power tothe ordinary locomotive. It would, there- 
fore, seem to be unnecessary to introduce intercepting 
valves, or other, and more complicated, starting arrange- 
ments. That the power of the compound locomotive at 
other crank positions is superior to that of the other will 
be made clear by an inspection of diagrams of crank posi- 
tions, such as Fig. 29. 

It has been shown that if the cranks of a French type of 
compound locomotive were placed at angles of 120 degrees 
the combined turning moment would be considerably im- 
proved, and it appears from an examination of a diagram, 
such as Fig. 29, that, with a starting gear of the Lindner 
or von Borries form, the starting power will be increased. 
As before, the most disadvantageous position for starting 
will be that at which one of the pistons has passed just be- 
yond the latest cut-off position. Thecranks of the other two 
pistons will then be at approximately 25 degrees and 85 de- 


COMPOUND LOCOMOTIVES. 109 


grees with the center line, and the combined crank effort 
will be equal to about 1.4 times the maximum of one cylinder 
as against about 1.13 times that of one cylinder for the 
most disadvantageous position with the arrangement of 
cranks actually used on this locomotive. The latter is, of 
course, the best disposition of cranks with the system of 
steam distribution which was adopted. It may be useful 
to note that on the assumption of a uniform steam press- 
ure throughout the stroke on all thiee pistons inversely 
proportional to their areas, the combined effort on the 
crank pins varies from 1.4 to 1.73 times the maximum 
for asingle cylinder for the 90 and 135 degree arrange- 
ment, and from 1.73 to 2 times the maximum for one 
cylinder for the 120 degree arrangement. 

In the Webb compound locomotive, as now built, no 
provision is made for admitting steam from the boiler 
directly to the low-pressure cylinder. The work of start- 
ing therefore devolves at first upon the high-pressure cyl- 
inders, which is equivalent to saying that the locomotive 
is primarily equivalent to a simple locomotive having 14 x 
24 inch cylinders and 175 pounds boiler pressure. It has 
been shown that the turning power on the cranks of the 
ordinary locomotive in starting may vary from about .75 to 
1.4 times the maximum for one cylinder, the lower limit 
corresponding to the position at which steam cannot be 
admitted to one cylinder. The tractive power of the Webb 
locomotive, of which the principal dimensions have been 
given, would then vary at starting from about .19 to .34 of 
the weight on the high-pressure driving wheels. It is per- 
fectly possible that the lower value may be encountered in 
practice, but it isnot probable, the case being about the same 
as that of an ordinary locomotive. The probability is that 
the high-pressure cranks will be in such positions that the 
tractive power at starting, with full boiler pressure on the 
high-pressure pistons, will be from .25 to .384 of the weight 
on the high-pressure driving wheels. If this is sufficient to 


110 COMPOUND LOCOMOTIVES. 


slip the driving wheels, steam will then be admitted to the 
receiver and so to the low-pressure cylinder until the press- 

ure in the receiver rises to such a point that the effective 

pressure on the high-pressure pistons is not enough to slip 
the wheels. The locomotive will then be in condition to 
start as a compound, all three cylinders being available. 

Another factor has now to be taken into consideration, 

which is the position of the low-pressure crank. Owing to 
the absence of coupling rods, this may be anywhere be- 
tween a dead point, in which position itis of course useless, 

and a half center where it can exert a pressure equal or 
superior to the combined high-pressure pistons. It is evi- 
dent that there is a wide range of possibilities in the start- 

ing power of the Webb locomotive, using the term starting 
power as we have heretofore in discussing two-cylinder’ 
locomotives. The exact starting conditions will be partly 
accidental, and partly dependent upon the skill of the en- 

gineer in stopping the locomotive in a good position for 
starting. 

The starting power of locomotives having the Webb ar- 
rangement of cylinders, but with the cranks at angles of 
120 degrees and coupled driving wheels, will be similar to 
that of the French type having a like disposition of cranks. 
Some form of starting valve would then be necessary or 
else the locomotive would be reduced, for all positions at 
starting, to a simple locomotive having two small cylinders 
and cranks 120 degrees apart. Without entering into a de- 
tailed investigation, which the practical value of this form 
of construction does not seem to warrant, it appears that 
two cylinders would always be available in starting, and 
that if one of these was the low-pressure cylinder, the loco- 
motive would have ample power, while if the low- 
pressure was unavailable, there would be an evident de- 
ficiency. 

THREE-CYLINDER LOCOMOTIVES IN PRACTICE.—The pub- 
lished records of the comparative performance of ordinary 


COMPOUND LOCOMOTIVES. 111 


and three-cylinder compound locomotives are not as com- 
plete as those for locomotives of the two-cylinder type. It 
is to be remembered, however, that any saving which has 
been effected by their use is not due to their having three 
cylinders, but is the result of the application of the com- 
pound principle, which necessitates a more economical use 
of steam in ordinary running. The following is a sum- 
marized statement of the work of compound locomotives 
on the London & Northwestern Railway, as given out by 
Mr. Webb in June, 1889. Seventy-five compounds had run 
11,644,222 miles since the introduction of the system in © 
1882, with an average fuel consumption of 32.9 pounds per 
mile. One éxpresslocomotive had run 154,342 miles in 
about 414 months on an average coal consumption of 36.5 
pounds per mile, including that burned while standing in 
steam or issued for all purposes. The average of forty of 
the same class was 86.8 pounds per mile. On the Metro- 
politan District Railway a converted locomotive had run 
178,337 miles on an average coal consumption of 23.2 
pounds, against 32.4 pounds average for six months for an 
ordinary locomotive doing the same work. 

A report of the results obtained with three Webb com- 
pound and three ordinary locomotives in India, doing the 
same class of work, for the month of Janury, 1886, shows 
an average coal consumption of 37.57 pounds per mile for 
the compounds, against 47.14 pounds per mile for the 
ordinary locomotives. The average mileage for the month 
was 2,448 and 1,700 miles respectively, 

No reports of fuel tests of the French three-cylinder 
locomotive have as yet been made public. It is reported 
as having hauled very heavy trains (Hngineering, Dec. 6, 
1889) up grades of 1 in 200at speeds of from 124 to 80 miles 
per hour, but the records do not appear to be valuable for 
comparison with American practice. It was found that 
the exhaust nozzle (4.21 inches in diameter) was too small 
for satisfactory work at the higher speed. 


112 COMPOUND LOCOMOTIVES. 


COMPARATIVE SUMMARY.—The reasons which would 
lead to the selection of the three-cylinder type of com- 
pound locomotive in preference to the two-cylinder form 
have been already mentioned. The better distribution of 
weights is obvious; it has been demonstrated that the 
combined turning moment is better, and the greater pos- 
sibilities in the direction of utilizing high boiler pressures 
economically are apparent, as we find a cylinder ratio of 
2.3 in the Webb locomotive and 2.68 in the French, which 
would be impracticable ratios for heavy two-cylinder loco- 
motives. To this may be added that with the French 
arrangement of cylinders it is possible to construct a very 
powerful and an economical locomotive, for which the 
low-pressure cylinders will be no larger than those now in 
common use. 

To offset these advantages we will have a cranked axle, 
a considerable increase in the number of parts and a con- 
sequent increase in first cost and expense of maintenance. 
It is not the intention of the writer to discuss the merits 
and demerits of cranked axles nor to advocate their use. 
But in view of the fact that there are hundreds of them in 
use on locomotives in Great Britain and in Europe, the 
necessity of using them should not stand in the way of a 
trial of three cylinder locomotives if other considerations 
make such a trial advisable. 

In this connection it should be noted that the Webb com- 
pound locomotive, probably from the fact that it has been 
the most widely illustrated of any type of compound, has 
apparently come to be regarded by many as the standard 
by which ail compound locomotives are to be measured. 
It has been unreasonably attacked and unjustifiably 
vaunted. The weak features in its design, from an Ameri- 
can point of view, have been charged to the compound 
system in general, and its successes credited to the per- 
sonal superintendence or ‘‘nursing” of the inventor. That 
the latter 1s a factor which is at least worth considering in 


COMPOUND LOCOMOTIVES. 113: 


estimating the value of the reported results, should be evi- 
dent to all who are familiar with the management of steam 
machinery. It will nct probably be questioned that a sup- 
erintendent of motive power can, by paying special per- 
sonal attention to some one item of expenditure, secure a 
notable saving therein, although it is not unlikely 
that this concentration of supervision may make 
more important losses possible. And it has 
been shown that a change in engineers may result in a 
greater saving of fuel than can ordinarily be expected to. 
follow the introduction of compound locomotives. But 
there is reason to believe that with the same handling and 
on the same work a properly proportioned compound 
locomotive, regardless of the ‘‘system” to which it be- 
longs, will be much more economical in the consumption 
of fuel than the ordinary locomotive. Whether it has 
two, three or four cylinders is a secondary matter. Its 
value as a fuel-saver compared with other means of econo- 
mizing lies largely in the fact that its success depends 
less upon the care and attention of the engineer than does. 
that of any device which can be added to the ordinary 
locomotive. Failures due to errors in design or to unsuit- 
ability for the service demanded do not form a sound basis 
for arguments against the practicability of applying the 
principles of compound working to locomotives. 


ORLA Re HEE coe 





FOUR-CYLINDER COMPOUND LOCOMOTIVES. 


There are two general classes of four-cylinder compound 
locomotives, one of which embraces all designs in which a 
receiver of large capacity is used, and in which the angles 
between the cranks are comparatively unimportant, while 
the other includes only those engines in which the high 
and low pressure pistons are on one piston rod, or are other- 
wise rigidly connected, and the ‘‘ dead space ” between the 
cylinder is reduced toa minimum. The first class includes 
those locomotives which have two inside connected high- 
pressure cylinders and two outside connected low-pressure 
cylinders, and also Mr. Mallet’s double bogie compound 
locomotive. The second class comprises tandem engines 
and those of the Vauclain type, in which the high and low 
pressure cylinders are placed side by side and both pistons 
are connected to one crosshead. 

The elementary theory of four-cylinder compound loco- 
motives of the first class is essentially the same as that of 
two-cylinder receiver engines, and the four-cylinder type 
may be regarded, as far as the cylinders are concerned, as 
formed from the two-cylinder type by substituting for 
each cylinder of the latter two cylinders having a joint 
volume equal to the corresponding single cylinder. It was 
shown in discussing two-cylinder receiver engines that, in 
making approximate calculations to determine proportions, 
the receiver pressure may be regarded as constant without 
serious error, assuming that the capacity of the receiver is 
large compared with that of a high-pressure cylinder. It 
follows from this that the distribution of work in the cyl- 
inders is practically independent of the angle between the 


COMPOUND LOCOMOTIVES. 115 


high and low pressure cranks when a large receiver is used. 
If in a four-cylinder engine both high-pressure cylinders 
exhaust into one receiver, which is the reservoir from 
which both low-pressure cylinders are supplied with 
‘steam, the variations in pressure in this receiver during a 
revolution will presumably be less than in a two-cylinder 
engine. Wecan, therefore, in the design of four-cylinder 
engines, make use of formulas which are based upon a 
constant receiver pressure, proceeding at first asif the en- 
gine were to have but twocylinders. The formulas are 
those which are usually given for two-cylinder receiver 
engines, and are notof special value in the design of two- 
‘cylinder compound locomotives on account of the necessity 
of a very careful analysis of the steam distribution in that 
type of locomotive if the possible advantages of compound 
working are to be realized. 

In subsequent formulas the letters have the following 
meaning: 

v = volume of high-pressure cylinder. 


V= ~*~ * low-pressure cylinder. 
R = ratio of the cylinders, V= Rv. 
y = ratio of expansion in h. p. cylinder. 
7’ — 66 6é 66 66 1. p- 6é 


p, = pressure in h. p. cylinder during admission. 

2 = pressure in h. p. cylinder when exhaust opens, 

3 = mean pressure in the receiver. 

‘¢ = pressure in l. p. cylinder during admission. 

4 = mean l. p. back pressure. 

All pressures are absolute pressures. 

Neglecting the effects of clearance, the mean forward 
pressure in the high-pressure cylinder is 


1+hyp. log. r 
ed alld I. cae ANS 


Pm S 


The mean effective pressure is (~Pm—>p,) and the work 
done in the high-pressure cylinder during a stroke is 


116 COMPOUND LOCOMOTIVES. 


U(Pm—p;). Similarly, the mean forward pressure in the 
low-pressure cylinder is, 
" 1 +- hyp. log. r’ 
f'n = Map log. 
the mean effective pressure is (p’m—p,) and the work done 
in the low-pressure cylinder during a stroke is V(p’m— p,). 
If the work is to be equally divided between the two 
cylinders, v (p m— pP3)=V (p’m —p,). 
On the basis that volumes vary inversely as the pressures, 
we have, 





8 


Piva tPsVEePs R 
eae ic Ta. 
By substituting the value for p, obtained from this. 
equation in the preceding one, and reducing, the following — 
is obtained: 


Pe 


ra log. No. = +p4= 0.4 

By means of this equation the ratios of expansion in. 
each cylinder (r and r’) for which the work done in each 
will be equal can be determined for any assumed values of 
p,p,and Rk. If it were required that there should be no: 
drop in pressure at the end of the expansion in the high- 
pressure cylinder, p, must equaz p,, from which it follows. 
that 7’ must equal R. It will be found that equation (4) 
will give impossible values for r’ for many values of 7, As 
r becomes less, or steam is admitted to the high-pressure 
cylinder during a large part of the stroke, r’ will be found 
to be less than one which is manifestly impossible, and 
shows that with a late cut-off in the high-pressure cylinder 
the work cannot be equally divided between the cylinders. 
On the other hand, as 7 is made large, 7” also increases. 
until it is greater than R, which is an impracticable result, 
as the receiver pressure would then be higher than the 
pressure in the high-pressure cylinder at the end of 
the expansion. For example, if we take R= 2.3, 
Pp, = 190 pounds absolute, p, = 20 pounds absolute, and. 


COMPOUND LOCOMOTIVES. 117 


v7 = 1.38, or cut-off at0.75 of the stroke in the 
high-pressure cylinder, the equation reduces to hyp. log. 
r’ + .4848 7’ = 0.3904 from which 7” = 0.97. As steam 
is admitted during the whole stroke when 7’ = 1.0, it is 
clear that with the above proportions more than one-half 
of the total work is necessarily done in the low-pressure 
cylinder. If ris taken as equal to 4, with the other data 
the same as before, the value of r’ will be found to be 
3.75, or the low-pressure cut-off would have to be placed at 
1 + 3.75 or (0.267 of the stroke. But as there will be no 





Baa te fA 
0 0.10 0.20 0.30 0.40 fp 0.50 0.60 0.70 0.80 
Fig. 41 


drop in pressure between the cylinders when 1’ = R, or 
when steam is cut off in the low-pressure cylinder at 1 + 
2.3 = 0.485 of the stroke, it follows that to equalize the 
work in the two cylinders at the earlier cut off the re- — 
ceiver pressure would have to be higher than the pressure 
at the end of the expansion in the high-pressure cylinder. 
The engineers of the Paris, Lyons & Mediterranean Rail- 
way have applied a formula similar to the above in the 
determination of the proportions for a class of four-cylin- 
der compound locomotives, and have shown the proper re- 


118 COMPOUND LOCOMOTIVES, 


lations existing between the points of cut-off in the high 
and low pressure cylinders graphically by a diagram sim- 
ilar to Fig. 41. This diagram is reduced from that given 
in a pamphlet by Mr. C. Baudry, assistant engineer-in-chief 
of motive power and equipment. Formulas similar to the 
above will be found discussed at greater length in ‘‘Com- 
pound Engines,” by Mr. Mallet; but in some editions of 
his book there are many confusing typographical errors. 
In Fig. 41 the horizontal distances represent the points of 
cut-off in the high-pressure cylinder, and the vertical 
distances represent the points of cut-off in the 
low-pressure cylinder. The inclined lines are curves 
‘which represent the solution of equation (4) for dif- 
ferent values of R, the pressures used in the construction. 
of the diagram probably being 213 and 21 pounds. For ex- 
ample, if A = 2.5 when the high-pressure cut-off is at. 
0.4, the low-pressure cut-off should be at about 0.5 
in order to equalize the work. If the ratio R = 2, 
a cut-off at 0.4 in the high-pressure requires a cut- 
off at about 0.58 in the low-pressure cylinder. For 
the cases in which the equation gives values 
of r’ which are too small, the cut-off for the low-pressure 
cylinder is fixed at 0.8 or the maximum for full gear. For 
instance, taking R = 2, the low-pressure cut-off would re- 
main at 0.8, or full gear for all values of the high-pressure: 
cut-off greater than 0.58, although more than one-half of 
the work would then be done in the low-pressure cylinder, 
The other limit to the application of the formula is fixed by 
making the earliest low-pressure cut-off that at which 
there will be no drop in pressure between the cylinders. 
So that finally, the relation between the points of cut-off in 
the two cylinders is shown by broken lines such as a bc d, 
for which R = 1.82. For example, if R = 2, the diagram 
shows that the points of cut-off should vary as follows: 


High-pressure... 4. whenss seer eee 10 .20 .30 .40 .50 .60 .70 .80: 
AiO W-PLESBULC ss csa Sosa cs ceiecs ces .50 .50 .50 .58 .70 .80 .80 .80 





120 COMPOUND LOCOMOTIVES. 


It does not of course follow that it will be advisable in 
practice to make use of the early cut-offs given above for 
the high-pressure cylinder, and it will be remembered that 
Mr. von Borries has stated, as the result of his experience 
with two-cylinder compound locomotives, that the most 
advantageous points of cut-off in the high-pressure cylin- 
der are from 0.3 to 0.4 of the stroke. 

Before calling attention to some of the special problems 
which wi!l present themselves in the design of four-cylinder 
compound locomotives, illustrations will be given of three 
experimental types which have recently been constructed 
by the Paris, Lyons & Mediterranean Railway, and which 
are described in the pamphlet by Mr. Baudry, to which 
reference has been made. Fig. 42 shows the general ar- 
rangement of the compound locomotives intended for fast 
passenger service. The principal dimensions of these 
Jocomotives, and of the type of simple locomotive which — 
formed the basis for the design, are given in the ac- 
companying table under the heading Fig. 42. The table 
shows that two compound locomotives of this and of each 
of the succeeding types have been built, which differ only 
in the number and diameter of the tubes. It will be seen 
that in the type of locomotive illustrated by Fig. 42 all 
four cylinders are placed beneath the smoke-box, witb their 
axes horizontal. The two high-pressure cylinders are 
between the frames and are connected to the forward 
driving axle. The low-pressure cylinders are con- 
nected to the rear driving axle. The axles are 
so coupled that the high-pressure crank on 
each side leads the low-pressure crank on _ the 
same side 198°. The object of this arrangement is to ob- 
tain as large a value for the minimum starting power as 
possible. In Fig. 43 is shown the general arrangement of 
the four-cylinder compound locomotives for freight service. 
In this locomotive the second driving axle is connected to 
the low-pressure cylinders, and the third axle to the high- 


COMPOUND LOCOMOTIVES. 





121 


122 COMPOUND LOCOMOTIVES. 


pressure cylinders. The high-pressure crank on each side 
leads the low-pressure crank 232° 48’. In the correspond- 
ing simple locomotive, of which the dimensions are given 
in the sixth column of the table, the rear axle is nota 
driving axle. Fig. 44 illustrates the arrangement adopted 
for locomotives for steep grades. The high-pressure cylin- 
ders are connected to the second axle, and the low-pressure 
cylinders to the third axle. The high-pressure cranks lead 
the adjacent low-pressure cranks, as in the other designs, 
but in this case the angle is 235° 54’, 

The Walschaert valve gear is used for all of these loco- 
motives, and the points of cut-off in the high and low- 
pressure cylinders are adjusted by means of a complicated 
cam arrangement, designed to fulfill the requirements in- 
dicated by Fig. 41. The starting gear adopted for these 
locomotives consists of simply an auxiliary steam pipe and 
cock for admitting steam from the boiler to the receiver, 
which is fitted with a safety valve as usual. In determin- 
ing the sizes of the cylinders the basis of calculation ap- 
pears to have been the weight of steam which the boiler 
may be expected to produce without being forced. This 
quantity had been found by previous tests to be about 
14,500 pounds per hour for the boiler of the express loco- 
motive, and the cylinders should be capable of dispos- 
ing of this weight of steam. Mr. Baudry 
states that the steam may, with due _ regard 
to the tractive power necessary, be expanded to 
a pressure of about 44 pounds absolute at a speed of 31 
miles per hour, and to about 19 pounds absolute at a speed 
of 68 miles per hour. The high-pressure cylinders should 
be capable of utilizing the above weight of steam at slcw 
speeds when the full tractive power of the locomotive is 
required and also at high speeds. The dimensions selected 
for the cylinders are thought to meet these requirements, 
the cut-off in the high-pressure cylinders being of course 
made earlier as the speed is increased. The method by 





124 COMPOUND LOCOMOTIVES. 


which the angles between the adjacent high and low-press- 
ure cranks were determined is not explained. Consider- 
ing the question of balancing the locomotive, the best re- 
sults would apparently be obtained by placing each high- 
pressure crank at 180° from the adjacent low-pressure 
crank. To obtain the greatest value for the minimum 
turning moment in starting, the angle between the high 
and low pressure cranks should be 225°, assuming that the 
pressure of the steam admitted directly to the receiver 
is such that the total pressure on each piston is the same, 
and that the cranks on each axle are at right angles. The 
angles which were adopted appear to be to acertain extent 
a compromise. For the express locomotive, Fig. 42, in 
which the question of the balancing of the reciprocating 
parts at high speeds would be of most importance, the 
angle selected, 198°, is approximately half way between 
180° and 225°. For the freight locomotive the starting 
power was apparently given greater weight in the prob- 
lem, the angles in each design being 225° plus the angle 
of inclination of the high-pressure cylinders. 

It will be interesting in this connection to note the rea- 
sons as given by Mr. Baudry for the adoption of such high 
steam pressures and the four-cylinder type. ‘‘The sole 
object of the study of new types has been to secure as great 
economy in fuel as possible. It has therefore seemed nec- 
essary to increase the boiler pressure considerably and to 
adopt the compound system. It is true that some saving 
in fuelcan be realized by the use of the compound system ° 
without increase of pressure; but the ultimate advantage 
seems to be in this case at least questionable. With the 
pressures of from 128 to 156 pounds per square inch used 
for locomotives, it is not necessary to resort to this system 
to obtain a large expansion. Its adoption could then only 
diminish to some extent the losses resulting from conden- 
sation in the cylinders; but as the difference between the 
extreme temperatures is not very great, and considering 


COMPOUND LOCOMOTIVES. 125 


the high piston speed, the economy which would 
result’ does not seem to be sufficient to compen- 
sate for the mechanical complication and_ the 
additional expense for repairs which it entails. With 
high pressures, on the contrary, a little more coal is re- 
quired to heat the steam, but the possible work of this 
steam when suitably expanded is increased in a much lar- 
ger proportion; but the expansion can no longer be accom- 
plished in a single cylinder with slide-valve distribution, 
the only method which seems to be practicable for locomo- 
tives; moreover, the variations in temperature are much 
greater, and the effect of condensation in the cylinder may 
become considerable. For these two reasons the compound 
system becomes a direct consequence of high-pressures in 
locomotives. It was thus that Mr. Henry was led, without 
any other reason, to adopt for the new P. L. M. engines the 
pressure of 213 pounds and the compound system. 

The employment of four cylinders is not a necessary conse- 
quence of the adoption of the compound system. Indeed, 
the greater part of existing compound locomotives in 
France and in other countries belong to the Mallet system, 
and have consequently only two cylinders. But the 
adoption of this system for locomotives as powerful as 
those under consideration would have led to very large 
dimensions, both for the cylinders and for their connec- 
tions. With four cylinders, acting two by two on differ- 
ent axles, these dimensions are more moderate; there is 
the further advantage of perfect symmetry, and what is 
still more important, a notable diminution in the strains on 
the driving axles and on the rails. The axles are less 
strained because each transmits but one-half of the work 
of the locomotive; and the strains on the rails are less 
since the rapid shocks due to the obliquity of the connect- 
ing rods are proportional to the efforts transmitted by the 
latter, and since these are one-half less when the same 
work is transmitted by four connecting rods instead of 
by two.” 


126 COMPOUND LOCOMOTIVES. 


We are indebted to the engineers of the Paris, Lyons & 
Mediterranean Railway for their very thorough investiga- 
tion of four-cylinder receiver compound locomotives, and 
the report on the performance of these locomotives will be 
awaited with interest. But the writer is not prepared to 
admit that all of the points in Mr. Baudry’s argument are 
well taken, or that the advisability of using the four- 
cylinder receiver type of engine has been demonstrated. 
A reference to the accompanying table shows that the 
weights of the compound locomotives are in all cases con- 
siderably greater than those of the corresponding simple 
engines, and they should therefore be more powerful, as 
they are in fact reported to be. But it does not appear 
that it was necessary to resort to this type of compound 
locomotive in order to secure the advantages of com- 
pound working. The adhesion weight and the diameter 
of the driving wheels of the compound express locomotive 
(Fig. 42) are nearly the same as in the Webb engine 
and in the Worsdell engine, which have been illustrated in 
these pages. The total weight of the four-cylinder locomo- 
tive is from nine to ten tons greater than that of the two 
and three cylinder locomotives, and there is, therefore, that 
much more dead weight. In the designs for the freight 
locomotives there is more reason for the use of four cylin- 
ders, although the three-cylinder.compvund locomotive 
of the Northern Railway of France, which we have illus- 
trated, is comparable with the simple locomotive of which 
the dimensions are given in the sixth column of the table. 
It certainly cannot be justly claimed that the necessary 
complication of two-cylinder compound locomotives of the 
von Borries, Worsdell, or Lindner types, is sufficient to 
have much weight as an argument against iheir use. Nor 
does it follow that pressures as high as 213 pounds per 
square inch are a necessity in order to secure good results 
from the use of the compound system. We have no ex- 
perimental data by which the advisable maximum and 


COMPOUND LOCOMOTIVES. 127 


minimum steam pressures can be determined, but we have 
reports of good economical results from two-cylinder com- 
pounds working with a steam pressure of kut 120 pounds. 
The economical advantages of compound working aoe in 
general more marked as the pressure is increased, but there 
is obviously a limit beyond which there will be no gain in 
economy by increasing the pressure. The reasons for 
this are similar to those which make the adoption 
of the compound system advisable in any case; briefly, that 
to secure the advantages of high-pressure steam it must be 
sufficiently expanded. Therefore, as pressures are in- 
creased, a point will be reached beyond which no greater 
proportion of the energy in the fuel can be utilized with 
two cylinders of practicable dimensions than can be utilized 
in a single cylinder with lower pressures. To secure full 
advantage of the high pressures, triple or quadruple expan- 
sion engines must be used as in modern marine practice. It 
is not, of course, to be inferred that it is advisable to con- 
struct triple or quadruple expansion locomotives, although 
such construction would seem to be more sensible than 
that of some of the ingenious monstrosities which appear 
perennially, and which frequently receive the favorable 
indorsement of men who should know better. We are not 
prepared to assert that such pressures as 213 pounds per 
square inch are too high for good work in compound loco- 
motives, but wish simply to call attention to the fact that 
there are both maximum and minimum limits to the press- 
ures which are properly applicable to compound engines. 

The principal advantages of the four cylinder receiver 
type of compound locomotives appear to be the possibility 
of obtaining a very uniform turning moment, together 
with a better running balance than is possible with any 
other form of locomotive. Whether or not these advan- 
tages are sufficient to compensate for the greatly increased 
number of parts must remain a matter of opinion. 

Mr. Mallet’s ‘‘ articulated” four-cylinder compound lo- 


128 COMPOUND LOCOMOTIVES. 


comotives do not present any special features as far as the 
steam distribution isconcerned. In this form the high- 
pressure cylinders are fastened to the rear part of the main 
frames, and drive one set of driving wheels, and the low- 
pressure cylinders are mounted on a front bogie with a 
second set of driving wheels. There is, therefore, no dead 
weight, and the locomotive is specially adapted for use on 
very sharp curves. At the same time, as the low-pressure 
cylinders are on the bogie, the joints in the steam connec- 
tions are not subjected to high pressure and therefore will 
not be difficult to keep tight. This system has been used 
with success on narrow gauge roads, while on the other 
hand it has been adopted for a locomotive for the St. Got- 
hard Railway, which weighs about 85 tons (2,240 pounds) 
in working order. There are six axles, coupled in two in- 
dependent groups, the low-pressure cylinders being placed 
with three axles on the front bogie, while the high-press- 
ure cylinders are fastened tothe main frames and are con- 
nected with the other three axles, 


COMPOUND LOCOMOTIVES. 

















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FOUR-CYLINDER COMPOUND LOCOMOTIVES, 


Tandem Engines.—The problems to be solved in connec- 
tion with the steam distribution in compound engines in 
which the pistons move simultaneously are in some re- 
spects quite different from those which are encountered in 
the design of compound receiver engines. The tandem ar- 
rangement is one form of what are frequently called 
Woolf engines, or continuous expansion engines, the dis- 
tinctive feature of the class being that the pistons move 
simultaneously, and that there is no receiver. In the sim- 
plest forms of this type, as applicable to locomotives, the 
high- and low-pressure pistons are attached to the same 
piston rod, and the slide valves of both cylinders are oper- 
ated by the same link motion. The peculiarities of the 
steam distribution in this arrangement of cylinders can be 
best examined by means of theoretical indicator cards, 
such as Fig. 45. Referring to this figure, a, D, d, e, f, g, 
h,k,ais the high-pressure card, and g, h,l, m, n, q, g is 
the low-pressure card. In the high-pressure cylinder cut- 
off takes place at 6, and there is expansion in that cylinder 
until the exhaust opens at d. There is then a drop in 
pressure to e as the steam in the high-pressure cylinder 
mingles with that in the passages which connect the cylin- 
ders. From eto f there is further expansion in the high- 
pressure cylinder and the connecting passages. At f the 
low-pressure steam valve opens and there is another drop 
in pressure to g. From g to hf the cylinders are in com- 
munication, and there is expansion until the low-pressure 
steam valve closesath. From h to k there is compression 
in the connecting passages and the high-pressure cylinder, 


131 


COMPOUND LOCOMOTIVES. 








eed 

_ | ! 
ft Fee 
Ree 

| 


Ny 
a 


132 COMPOUND LOCOMOTIVES. 


and when the high-pressure exhaust closes at & there is 
further compression in that cylinder. In the low-pressure 
cylinder the steam expands from h to 1 where release 
occurs and the pressure drops to the ordinary back press- 
ure line. 

The features of this diagram which require special at- 
tention are the losses in pressure at d and / and the com- 
pression in the high-pressure cylinder. In order to prevent 
the drop at d, either the pressure in the connecting pas- 
sages when the high-pressure exhaust opens must be the 
same as that at d, or else the volume of the connecting 
passages must be practically nothing. The former result 
can possibly be obtained by adjustments of the low-pres- 
sure cut-off, but it is not practicable on account of the 
unavoidable complications. The only feasible method of 
reducing this loss to an inappreciable amount appears to 
be to make the volume of the connecting passages very 
small compared with that of the high-pressure cylinder, 
The drop in pressure at f can be prevented or reduced by 
compressing to the pressure f in the low-pressure cylinder, 
or by making the low-pressure clearance very small. 

The question of compression in the high-pressure cylinder 
in this type of engine iseven more troublesome than in 
receiver engines, In order to avoid compressing to a 
higher pressure than the initial pressure with the usual 
forms of valve gear, it is necessary that the volume of the 
high-pressure clearance space should be made large, since 
the pressure at k, where the compression caused by the 
exhaust closure begins, is unavoidably high. This pressure 
can of course be somewhat reduced by making the volume 
of the passages connecting the cylinders large, but, as has 
been shown, this involves a considerable drop in pressure 
atd. The expedient of giving the high-pressure valve in- 
side clearance may also be employed in connection with a 
large clearance space to assist in keeping down the com- 
pression. In any case in which the shifting link motion is 


COMPOUND LOCOMOTIVES. 133 


used early cut-offs are to be avoided, both on account of 
this compression and o avoid the wiredrawing which re- 
sults from a small port opening. 

lt is, however, not necessary to resort to very early cut- 
offs in order to obtaina sufficiently great expansion, as 
this may be secured by using a comparatively large cylinder 
ratio. If, for example, we assume a cylinder ratio 3 anda 
boiler pressure of 160 pounds, a final pressure of about 2.5 
pounds above the atmospheric pressure can be secured with 
a cut-off in the high-pressure cylinder at three-tenths of the 
stroke at slow speeds, and at high speed a later cut-off 
would be necessary to maintain the same terminal 
pressure. 

In determining the proportions for the valve gear and the 
size of the cylinders advisable for a tandem compound 
which is intended to take the place of an ordinary locomo- 
tive, the most satisfactory mode of procedure will be to 
construct theoretical indicator cards, using the term as we 
have heretofore, for various points of cut-off, measure the 
area of these cards or calculate them by the formulas al- 
ready given in discussing the theory of two-cylinder re- 
ceiver engines, and finally to adjust or ‘‘ doctor” the cards 
for losses, as experience with ordinary locomotives has 
shown to be necessary. Anexample of indicator cards 
constructed in this way is given in Fig. 45,0n a much 
smaller scale, however, than is advisable in practice. The 
assumed data in this case are as follows: Initial pressure, 
175 pounds absolute; cylinder ratio, 3; low-pressure back- 
pressure, 17 pounds absolute; cut-off in both cylinders, 0.5; 
release and compression in both cylinders, 0.78; volume of 
high-pressure clearance, 15 per cent.; volume of low-pres- 
sure clearance, 6 per cent.; volume of connecting passages, 
0.3 of high-pressure cylinder. The scale of pressures used 
in the diagram is 80 pounds tothe inch. For the benefit of 
those who may wish to construct such diagrams we will 
follow through this case in some detail. 


134 COMPOUND LOCOMOTIVES. 


‘The following symbols will be used: 
v = volume swept by high-pressure piston. 


ge = 4) 4 ‘* low-pressure a 

C= ‘* of high-pressure clearance. 

C= ‘* of low-pressure “ 

tox ‘* of intermediate or connecting passages. 


The volumes occupied by thesteam at the several lettered 
points on the diagram are, then, 

Atb,= 5v+c=.6dv, 

Atd, = .78v+c= .93 v. 


Atf, =vtc+t7=1.45v. 

Atg, =1.45v+ C= 1.63 v. 

At h, before cut-off, = 5u+e+i+C+.5V= 2.638». 

Ath, in 1. p. after cut-off, = .56 V+ C= .56 V. 

Ath, inh. p. and passages after cut-off inl. p., = .6v + 

c+t= .95v, 

At k, before valve closure, = .22v+e +7 = .67 uv. 

Atk, inh. p. after valve closure, = .22v+¢ = .37v. 

Atl,=.78V +0 = OY. 

Atn, = 22 V+ C= .28 V. 

The pressure at d and the curve between b and d may be 
found by constructing the curve through b with Bas the 
origin, A B being ,15 of A D;.or by calculation as the pres- 
sures may be taken inversely as the volumes, whence 
pressure at d = 175 X .65 + .93 = 122.3 pounds. The 
drop in pressure from d to e depends upon the pressure at 
k, that in turn depends upon h, and so upon g. The 
pressure at g depends upon that at g and at f/, and so upon 
e. Inany case, there is but one pressure at h which will 
fulfil the conditions, and that pressure must be determined 
by calculation. Assuming for the moment that we know 
the pressure at e to be 112.5 pounds, the pressure at f will 
be 112.5 K 1.23 + 1.45 = 95.4 pounds. The pressure at g 
is determined by the mixture of the volume at f at 95.4 
pounds with the volumeof the low-pressure clearance at 


COMPOUND LOCOMOTIVES. 135 


pressure g. To find the latter we have pressure at g = 

17 X .28 + .06 = 79.3 pounds. Then pressure at g = 
79.8 x .18 + 95.4 x 1.45 

18 + 1.45 
The pressure at h = 93.7 X 1.63 + 2.63 = 58.1 pounds. 
The pressure at k = 58.1 X .95 + .67 = 82.3 pounds. We 
can now find the pressure at e which is 
122.3 x .93 + 82.3 x .3 
93 + .3 

By combining these various expressions for pressures 
wecan readily form a single equation from which the 
pressure at h can be calculated, which is, in fact, the 
method by which it was determined in this case. 

Having found the pressures at e, g and h by calculation, 
the various curves of the diagrams can be readily con- 
structed. For the curve between e and f a point C is used 
for the origin, which is found by laying off B O equal to 
.80f AD. Thecurvehkis constructed from the same 
origin. The compression curve k wu is laid off from B. To 
find the origin for the curve gh, we proceed as follows: 
At g the steam occupies the volumev + c+ i+ (0, and 


= 93.7 pounds. 


=e L120, 


at h the volume occupied is .J5v+cec+i+C+4+ (5V= 


\ 


1.5v), The increase in volume is therefore equal to v, and 
therefore the scale of this part of the diagram must be 
such that the horizontal distance from g to h represents v, 
the volume of the high-pressure cylinder. With this 
scale of volumes lay off DK = .06V = .18v, K L = .3v, 
LN=vand NE = .15v; then EF 1s the origin from which 
to construct the curvegh. For the curves h/ and nq 
the origin is taken at H, whichis found by laying off 
D H= .06 of A D, which for these curves represents the 
volume of the low-pressure cylinder. 

This diagram illustrates the difficulty of keeping the high- 
pressure compression within reasonable limits. The ex- 
haust closure at 0.78 when cutting-off at .5 is approximate- 
ly that obtained with the valve gear, of which the distri- 


136 COMPOUND LOCOMOTIVES. 


bution was shown in tabular form in the Third Chapter. 
The valve has 0.25-inch inside clearance, and there is 15 
per cent. cylinder clearance. But the pressure at k is 82.3 
pounds, and the pressure at the end of the compression u 
will therefore be 82.3 x .87 + .15 = 203 pounds absolute, 
or 28 pounds above the initial pressure. To overcome this 
difficulty it will probably be necessary in most cases to 
make use of a combination of inside valve clearance, large 
cylinder clearance and considerable lead. 

As a first approximation in determining the size of cylin- 
ders the following method may be used. Assume, for 
example, that a tandem compound is to be substituted for 
an 18 X 24 simple locomotive, the same boiler pressure of 
160 pounds to be retained. With a cut-off at seven-eighths 
of the stroke, and 160 pounds initial pressure, the mean 
forward pressure in the high-pressure cylinder will be 
173.3 pounds absolute, and the final pressure in that cylin- 
der will be 153.1 pounds absolute. We may assume a drop 
in pressure of about 5 pounds between the cylinders on 
account of resistance of ports, etc., so that the initial 
pressure in the low-pressure cylinder may be taken at 148 
pounds. With acylinder ratio of three, the steam which 
now fills the high-pressure cylinder and the low-pressure 
clearance will be expanded to about three times its pres- 
ent volume, and the mean forward pressure in the low- 
pressure cylinder will be 81.3 pounds absolute. These mean 
pressures are calculated by the formulas already given in 
discussing the theoretical distribution in two-cylinder re- 
ceiver engines. The low-pressure back pressure may be 
taken at 17 pounds absolute, which gives 64.38 pounds for 
the mean effective pressure in the low-pressure cylinder. 
For our present purposes we will take the mean high- 
pressure back pressure as five pounds above the mean low- 
pressure forward pressure, which will give a mean effective 
pressure in the high-pressure cylinder of 173.3 — 86.3 = 
87.0 pounds. If the maximum mean effective pressure 


COMPOUND LOCOMOTIVES. 137 


which can be developed in the cylinders of the simple 
locomotive be taken as 155 pounds, we will have, in order 
that the maximum work of both engines may be the same, 
assuming that the stroke is the same in both, 87. a + 64.3 
x 3 a = 155 X 254.5, in which a is the area of the 
high-pressure piston and 254.5 is the area of the 18-inch 
- piston. From this equation we find a = 140.9 square 
inches, from which the area of the low-pressure piston is 
422.7 square inches. The corresponding diameters are 
approximately 13.4 and 23.2 inches. 

In the above approximate calculation, the effects of early 
exhaust opening, clearance, compression, and low-pressure 
cut-off have been neglected, and it will be apparent that a 
calculation in which these factors were duly considered 
would be very laborious. But knowing the approximate 
dimensions of the cylinders the design can be sufficiently 
completed to determine the volume of ports, passages, etc., 
and accurate indicator diagrams can then be constructed, 
by the method already given, by which the final dimensions 
for cylinders and valves can be determined. 

The starting power of a tandem compound locomotive, 
having cylinders of the dimensions given above, will be 
about the same as that of the simple 18 x 24 locomotive, 
when steam at about 82 pounds absolute pressure is ad- 
mitted directly to the low-pressure cylinders; The steam 
so admitted acts as forward pressure on the low-pressure 
pistons, and as back pressure on the high-pressure pistons, 
so that the locomotive may be said to start as a compound 
engine. There would, therefore, be no advantage in 
keeping the starting valve open after the first exhaust from 
the high-pressure cylinder had taken place. But there is 
another view of the question of starting which should be 
noted. If full boiler pressure were admitted to the high- 
pressure cylinder by the main steam pipe, and the same 
pressure to the low-pressure cylinder by means of the 
starting valve, the high-pressure piston would be 


188 COMPOUND LOCOMOTIVES. 


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145. 
Cut-off .7 
Revolutions, 61, 
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Cut-off .55 


Revolutions, 86, 


0. 





Fig. £8 





COMPOUND LOCOMOTIVES, 139 








Cut-off .45 


Revolutions, 86, 


0. 
Fig. 49 


Cut-off 55 





Revolutions, 192, 


Fig. 50 





Cut-off .36 


Revolutions, 82, 


140 COMPOUND LOCOMOTIVES. 


practically thrown out of action, and the starting power 
would depend simply upon the area of the low-pressure 
piston. Therefore, if this piston were but 18 inches in 
diameter, the possible maximum starting power would be 
equal to that of the simple engine. Such an engine as 
this would be deficient in power as a compound,. while 
with an engine having cylinders proportioned for the 
maximum pressure, as already given, it might be neces- 
sary to employ earlier cut-offs for ordinary work on a level 
than are advisable. 

It is probable that the best dimensions for cylinders will 
be found to be those which will permit the engine to do 
the greater part of its work at cut-offs of from .4to.5 in 
the high-pressure cylinder. It is evident that the only 
starting gear necessary is an arrangement by which steam 
can be admitted directly to the low-pressure cylinder for a 
short time in starting. 

A successful application of the tandem form of com- 
pound engine to a locomotive has been made by Mr. G. Du | 
Bousquet, of the Northern Railway of France. <A detailed 
description of this locomotive is given in the Revue 
Générale des Chemins de Fer for November, 1888, from 
which the illustration and indicator cards which follow 
have been taken. This locomotive is an eight-coupled out- 
side connected engine, all of the weight being on the . 
driving wheels. It was originally a simple locomotive, — 
having cylinders 19.68 inches in diameter by 25.59 inches 
stroke. The boiler pressure of 142.2 pounds, gauge, is the 
same as before converting it. The principal dimensions of 
this locomotive are as follows: 


Diameter of high-pressure cylinders Aslatew ea aitareatieees 15 inches 
loW=pressure 17a ee oc hac onl eer SF 26 oS 

Stroke'of pistons 4 .2...S.cchs oe se ete tec as enaenanee 2:6 

Diameter of driving wheels.........ccccscce-coscecese Vee. 

Total weight, all on driving wheels..............eeee- 113,970 mo Psa. tt 

Ares Of Crate <a 3.cc fcc sce abeon wee hae ous tine sive trea 

Total heating BUriates:.. ...0ssoscue sae Reo eee nee 1,356 ae et : 


The changes in the distribution and amount of the 


COMPOUND LOCOMOTIVES. 141 


weights on the axles on account of converting are given 
as follows : 





Simple. Compound. 

First axle........ Bo daiaeeces Rise acters ae ae 26,900 29,670 
Second axle........... SARC MSCS Siabieniete ae 24,470 31,390 
INCA IO a2 o/c see's’ sees Sue ee OP eee, 26,670 30,820 
eI E MESO dss cn sas orn ce sneyc 5 oa bis acne 20,500 22,090 
PEO CS tera aie.d aieicare sei sialcie aeleesieciae 98,540 113,970 


To balance the increased weight of the cylinders a foot 
board weighing 6,600 pounds was put in. Fig. 46 illus- 
trates the arrangement of the cylinders and valve chest, 
and is worthy of careful examination. It will be seen that 
the steam distribution for both cylinders is controlled by 
one valve, the low-pressure valve being, as it were, inside 
of the high-pressure valve. The arrows clearly indicate 
the paths of the steam. The frincipal dimensions relating 
to this valve gear are as follows : 


Travel of Valve........sessesesenee Ccevecvescccsce 6.22 ins 
Steam Jap, both cylinders, front...............6 34° 
“ ty o Ps WCE esis sede i eee. ° 1722 7 
Exhaust lap, high-preseiresc acc peck sty ee yoni s 0.00 ‘ 
= Pitt HIWEHTIVORS ULE ved vtistanisicic' ccc e wieiee 06 A 0:32 * 
Ports, high-pressure St€aM...... .csseeeees ceaee 17.72-ins, X 1.38 * 
PMO W -DECRSULG) "lich nes csees ect sa ness en ieee wi aoe 
ee lie ns OXHAUSE...5.. 2 sscccesssceee 17.72 °° xX 3.54 “ 
Angular advance of eccentrics ................. 30 deg. 
Clearance, per cent. of cylinder volume Be Dick ar 


Volume of connecting passages, per cent. PF h. p. volume., 16.5 

The features of this design which are specially note- 
worthy are that the dead space between the cylinders is 
reduced to a minimum, the high-pressure clearance space 
is large, and that there are no bushings between the cylin- 
ders, but instead there are outside stuffing boxes which 
are easily accessible. 

The indicator cards shown by Figs. 47 to 51, inclusive, 
illustrate the steam distribution in this locomotive. The 
effect of piston speed upon the distribution is well illustrat- 
ed by Figs. 48 and 50, which were taken at the same nom- 
inal point of cut-off, but as the two pairs of cards are ap- 


142 COMPOUND LOCOMOTIVES. 


parently from opposite ends of the cylinders, it is probable 
that the great increase in compression shown in Fig. 50 is 
partially due to irregularity in the valve motion. The mean 
pressures in these diagrams and the percentage of the total 
work done in the high-pressure cylinder are as follows, the 
pressures being taken from the tables in the Revue, as pre- 
viously noted: 


Mean pressure. Per cent. of work 
H. p. L. p. done in h. p. 
Wigs Siac cetecse os aes eee 79.36 30.87 46.2 
SAR kk oo ean pe Magia Ce 63.01 21.76 49.1 
oe AK Bi dead sts siete aaa 51.20 15.36 52.6 
OS BO cous. .0 salen Oeik gomen tutte sais o 36.84 15.22 44.7 
SO NGL heck tis, sein MAES a eee 31.86 9.53 52.7 


This locomotive has been carefully tested in comparison 
with a simple locomotive belonging to the same original 
class, and the results are recorded at considerable length in 
the issue of the Revue, to which reference has already been 
made. The compound hauled trains about 12 per cent. 
heavier than the simple locomotive, with a noticeable sav- 
ing in fuel, while with trains of the same weight the saving 
in fuel, as reported by Mr. Du Bousquet, was from 13.5 to 
25.8 per cent. The average of five tests is 21.9 per cent. 


CELA THe ssl. 





COMPARATIVE SUMMARY.—Having discussed the theoreti- 
cal principles of the several forms of the compound engine 
which are upplicable to locomotives, and having called at- 
tention in detail to the numerous conditions which control 
the application of these principles, we will now present a 
summarized statement of the factors which require special 
care in the design of compound locomotives, and will call 
attention to some minor points which have not been 
touched upon in the preceding chapters. 

It kas been shown that the first requisite in attempting 
the design of a compound locomotive is detailed informa- 
tion concerning the work which is to be demanded of the 
engine. This is necessary in the first place, because the 
chief object in introducing compound locomotives is econo- 
my, which can be secured in any engineering work only 
with full and accurate knowledge of the subject in hand, 
and in the second place, because, as we have seen, the 
compound engine is not as flexible as the simple engine, 
although it is sufficiently elastic te be successfully used for 
any class of railroad work when originally intended for 
that service. 

In the selection of a type of engine there will generally 
be considerable opportunity for individual preference. 
The two-cylinder type is unquestionably the simplest, but 
the large dimensions of the low-pressure cylinder, for a 
locomotive, may make the adoption of one of the other 
forms desirable. If the two-cylinder type is chosen, there 
is still room for individual opinion in the selection of a 
form of starting gear and in the determination of the size 
of cylinders, which will depend toa certain extent upon 


144 COMPOUND LOCOMOTIVES. 


the nature of the starting mechanism. Assuming that the 
maximum cylinder power as a compound is to be fully 
~ equal to the adhesion under the most advantageous circum- 
stances, the conditions are about as follows: With a start- 
ing gear consisting of simply a valve and connections for 
admitting steam at reduced pressure to the receiver, the 
locomotive in effect starts as a compound, and the cyl- 
inders must be proportioned on that basis. But on the 
other hand, the cylinders must not be made so large that 
it will be necessary to cut off very early, or to reduce the 
initial pressure much by throttling, in those cases in which 
the tutal pressure required on the pistons is comparatively 
small, as, for example, when simply maintaining speed on 
a level track. The final pressure in the low-pressure cyl- 
inder must not be permitted to fall below the atmospheric 
pressure, and the engine should be proportioned to do the 
greater part of its work, according to Mr. von Borries, at 
from 0.3 to 0.4 cut-off in the high-pressure cylinder. 

If an automatic intercepting valve is used, the effective 
pressure per square inch of piston may be increased in 
starting, but the locomotive will begin to work as a com- 
pound after from one-half to one and one-half revolutions 
of the driving wheels, depending upon the positions of the 
pistons, and the form and proportions of the intercepting 
valve, starting valves, and passages. The cylinders must 
be proportioned to do the maximum work which may bere- 
quired after compound working begins. If the original 
Mallet system is adopted, the locomotive can be worked as 
a simple engine as long as desirable, and the cylinders may 
be made somewhat smaller than with the other starting 
devices. This system appears to be specially applicable to 
converted engines, as one cylinder may be retained for the 
high-pressure cylinder without necessary increase in boiler 
pressure. 

In two-cylinder-engines the total work can be very nearly 
equally divided between the cylinders by arranging the 


COMPOUND LOCOMOTIVES. 145 


valve gear so that the cut-off in the high-pressure cylinder 

-is somewhat earlier than that in the low-pressure. The 
turning moment on the driving axle will be more nearly 
constant in a well-proportioned two-cylinder compound 
than in a simple locomotive, because for the same mean 
effective pressure the cut-off in each cylinder of the com- 
pound will be later than inthe simple engine. This possible 
advantage may be lost by improper valve adjustments 
which permit excessive compression and a very unequal 
division of work between the cylinders. 

To avoid excessive compression, particularly in the high- 
pressure cylinder, with the ordinary link motion, inside 
valve clearance, considerable lead, and large cylinder clear- 
ance may be necessary. Thequestionof the proper amount 
of compression in order to secure the most economical 
results is one which need not: be discussed in this connec- 
tion, as the problem which confronts the designer of 
compound locomotives is how to prevent the pressure at 
the end of the compression from exceeding the initial press- 
ure. 

The tandem form of four-cylinder compound locomo- 
tive would seem to be next to the two-cylinder type in 
simplicity. The number of pistons is doubled but the 
steam distribution on each side of the engine may be con- 
trolled by one valve, and there is no increase in the number 
of connecting-rods, eccentrics, etc. The additional com- 
plication is almost entirely in the valves, ports, and cylin- 
ders, and not in the driving connections, so that while the 
~ first cost will be greater, there is little reason to anticipate 
much increased cost for repairs. In the design of tandem 
engines the factors which demand special attention are the 
probable increase in the weight of cylinders, the compres- 
sion in the high-pressure cylinder, the drop in pressure be- 
tween the cylinders, the increased. weight of reciprocat- 
ing parts, and the protection of the cylinders from loss by 
radiation. The last item is specially important in this class 


146 COMPOUND LOCOMOTIVES. 


of engines as there is no opportunity for drying out the 
steam between the cylinders. The division of work be- 
tween the cylinders is comparatively unimportant. The 
great advantage of this arrangement of cylinders lies in 
the opportunity which it affords for the realization of great 
power together with economy without the employment of 
exceedingly large cylinders and with but two sets of rods, 
links, eccentrics, etc. The problem of starting power offers 
no difficulties in this type of engine. 

The three and four cylinder compound locomotives with 
receivers have many points in common with the two- 
cylinder form. The sole advantage of the Webb engine 
appears to be the absence of coupling rods. The three- 
cylinder type, having one high-pressure cylinder and two 
low-pressure cylinders, together with the four-cylinder 
receiver engines, have the advantage of a very uniform 
turning moment and an excellent balance, with the disad- 
vantage, common to all these forms, of much complication 
and consequent increased first cost and expense of main- 
tenance. 

PISTON SPEED— WEIGHT OF RECIPROCATING PARTS.—It 
has been urged by opponents of compound locomotives 
that, while there are admitted advantages in compound 
working with the ‘‘ slow piston speeds” found in marine 
and stationary engines, the high piston speeds found in 
locomotives make compounding a doubtful experiment. 
As a matter of fact, there are large triple expansion marine 
engines running at piston speeds of over 800 feet per 
minute. The piston speed attained by the quadruple expan- 
sion engines of the torpedo boat ‘‘ Cushing” was 925 
feet per minute on her trial, and the _ speed of 
pistons of the triple expansion engines of a recent Turkish 
torpedo boat is given as 936 feet per minute on a trial trip. 
If these speeds are practicable with triple and quadruple 
expansion engines, there does not appear to be any good 
reason for doubting the practicability of speeds of 1,100, or 


COMPOUND LOCOMOTIVES. 147 


even 1,400 feet, with compound engines. There is un- 
doubtedly a maximum limit to piston speed,.and it is 
lower for compound engines than for simple engines using 
the same boiler pressure. But the limit is sufficiently high 
to be comparatively unimportant to the designer of loco- 
motives. The cause which limits the speed is the weight 
of the reciprocating parts. In an engine working ata 
speed of 250 revolutions per minute, the reciprocating 
parts must be started from a state of rest at the beginning 
of each stroke, and their speed accelerated to about 26 
feet per second during approximately a half stroke, which 
occupies about 0.06 second. The method of calculating the 
necessary steam pressure per square inch of piston to 
produce this acceleration need not be explained in these 
pages, as it does not relate distinctly to compound 
locomotives. A very full and complete discussion 
will be found in a paper by Mr. D. S. Jacobus, 
in Vol. XI. of the Transactions of the American 
Society of Mechanical Engineers. Taking Mr. Jacobus’ 
figures, the pressure per square inch of piston for a loco- 
motive having a cylinder 18} inches in diameter and 24 
inches stroke, required to overcome the inertia of the recip- 
rocating parts and accelerate them at 250 revolutions per 
minute, varies from about 55 pounds at 10 degrees from 
the dead point to 0 at about 80 degrees. The work stored 
in the reciprocating parts during the first half of the stroke 
is of course transmitted to the crank-pin during the last 
half of the stroke, but the effective pressure on the crank- 
pin during the first half stroke is only that due to the dif- 
ference between the apparent pressure as shown by the in- 
dicator card and that necessary to accelerate the recipro- 
cating parts. It is evident that if the pressure of the 
steam on the piston is just equal to that required for ac- 
celeration at any position of the piston, no pressure will be 
transmitted to the crank-pin at that point in the stroke, 
and that if these pressures are equal during the period of 


148 COMPOUND LOCOMOTIVES. 


acceleration, all pressure which is transmitted to the 
crank-pin during the stroke will be during the second half 
stroke. The maximum piston speed of the engine will 
then be practically not far from that at which this occurs. 
The pressure necessary to produce acceleration varies 
directly as the weight of the reciprocating parts, and as 
the square of the speed of rotation. The possible means of 
reducing this pressure are therefore to make the recipro- 
cating parts lighter, or the driving wheels of greater 
diameter. How much the distribution of pressures on the 
crank pins will be affected by such changes is a question 
which must be solved by the designer in each case, and it 
is a factor which is worth careful consideration, more on 
account of the crank pin pressures than on account of the 
limitations of speed. A considerable reduction in weight 
is effected by the use of steel wherever practicable for the 
reciprocating parts, and the adoption of the most economi- 
cal shapes for connecting and coupling rods. In this con- 
nection the illustrations of recent two-cylinder compound 
locomotives in Engineering for Feb. 1, 1889, June 21, 1889, 
and Feb. 7, 1890, are worthy of careful consideration. 
Economy.—The principal reasons why a compound loco- 
motive should be more economical than a simple locomo- 
tive may be briefly summarized as follows: More economical 
use of steam by greater expansion; reduced loss from cylin- 
der condensation: better steam distribution on account of 
later cut-offs, and decreased demand upon the boiler. The 
commercial economy of the locomotive is the combined re- 
sult of these causes and also frequently includes a gain by 
reason of the increased boiler pressure. It is probable that 
we may add to the above reduced cost of repairs on ac- 
count of less rapid depreciation of the boiler and more 
uniform strains on pins and axles. The gain by greater ex- 
pansion and less loss by cylinder condensation is common to 
all multiple-cylinder engines, and the reader is referred to 
works on the theory of the steam engine for detailed dis- 


COMPOUND LOCOMOTIVES. 149 


cussion of these subjects. Among the many books which 
are valuable may be mentioned, in addition to those pre- 
viously referred to in these pages, ‘‘The Steam Engine,” by 
Prof. W. D. Marks, and ‘‘The Steam Engine,” by Prof. J. 
H. Cotterill. 

TESTS IN Russia.—Since the table of reports of com- 
parative tests of two-cylinder compound locomotives given 
in the Sixth Chapter was prepared, Mr. Thomas Urqu- 
hart, Locomotive Superintendent of the Grazi & Tsaritsin 
Railway, in Southeast Russia, has made public the results 
of his tests of compound locomotives in a paper read be- 
fore the Institution of Mechanical Engineers, England, 
which was published in full in Engineering of Feb. 21 and 
March 7, 1890. 

This paper is particularly interesting, as all of the en- 
gines tried were converted from simple engines, without 
increase of boiler pressure. The following is a brief ab- 
stract: 

An experimental converted engine was put to work in 
- September, 1887, and on trials against a simple locomotive 
did the same work with a consumption of 22 per cent. less 
of petroleum refuse. This result was so satisfactory that 
other locomotives were converted, and in December, 1889, 
there were in daily use twelve six-coupled freight engines 
and three four-coupled passenger engines. It is intended 
to convert the remainder of the locomotives on the line to 
compounds as fast as the shop facilities will permit. The 
mean consumption of petroleum refuse per engine mile for 
freight engines for ten months of 1889 is given in a table 
as 30.65 pounds for simple locomotives and 25.4 pounds 
for the compound locomotives. The mean saving in fuel 
is therefore 17.1 per cent. From April to August, inclusive, 
the saving by five compound freight engines ranged from 
14.75 to 25.57 per cent., the average being 18.96 per cent. 
A compound passenger engine saved in the same period 
18.22 per cent. Mr. Urquhart’s conclusion is that 18.5 per 


150 COMPOUND LOCOMOTIVES. 


cent. may be safely taken asthe saving by compound com- 
pared with ordinary locomotives. Inconverting these loco- 
mo.ives one of. the original cylinders was retained for the 
high-pressure cylinder, and the former boiler-pressure of 
135 pounds was also retained. 

The dimensions of some of these locomotives are as fol- 
lows: Cylinders, 18} inches and 25g inches in diameter by 
24 inches stroke; six coupled driving wheels, 51 inches in 
diameter; adhesion weight, 36 tons; tubes, 151, outside 
diameter, 24 inches; length between tube plates, 13 feet 
104, inches; heating surface, total, 1,281 square feet; grate 
area prior to using petroleum, 17 square feet; Stephenson 
link motion; maximum travel of valves, 4% inches; angu- 
lar advance of eccentrics, 20 degrees; high-pressure valve, 
outside lap, 0.81 inch; inside clearance, 0.08 inch; low- 
pressure valve, outside lap, 0.67 inch; inside clearance, 0.0. 
The author found that a very small difference in lap, out- 
side or inside, amounted to a great deal in fuel consump-: 
tion. In more recent locomotives the low-pressure link 
hanger has been made $ inch longer than the high-pressure 
hanger. 

The starting gear adopted and illustrated is of the Mallet 
type, being wholly under the control of the engine runner. 
A cock is provided for admitting steam from the boiler to 
the receiver, and there isa separate exhaust from the 
high-pressure cylinder to the atmosphere, the exhaust pipe 
being placed outside of the smoke box on the high-pressure 
side. The opening into this pipe is controlled by a plain 
disk valve, operated from the cab. A flap valve prevents 
the steam in the receiver from escaping back through this 
pipe or to the high-pressure cylinder, and is connected so 
as to be worked by the same lever as the above-mentioned 
exhaust valve. 

It was found by trials that these converted locomotives 
were capable of hauling as heavy trains as the simple loco- 
motives. With the reverse lever in the same notch in both 


COMPOUND LOCOMOTIVES. 151 


classes of engines, the power of the compound was found 
to be less than that of the simple engin®, the difference in- 
creasing as the cut-off was made earlier, from 5 per cent. 
in full gear to 28 per cent. in the ‘first notch” in the 
freight engines. The volume of the receiver was made 
equal to that of the high-pressure cylinder in the earlier 
engines and in the later designs was increased to 1.3 and 
then to 1.8 times the volume of the high-pressure 
cylinder, with good results. 

1t may be well to note that there is nothing contradic- 
tory in these results of Mr. Urquhart’s experiments to what 
has already been said concerning the power of two-cylinder 
locomotives. With thetype of starting gear adopted. the 
engine cannot be deficient in starting power if originally 
well proportioned, and after starting there is no difficulty. 
The mean pressure with any given cut-off in the high- 
pressure cylinder is necessarily less than in the simple en- 
gine with the same cut-off and the same boiler pressure, 
since the expansion is greater in the compound. 

Mention was made in a previous chapter of the reported 
advantage found by Mr. Urquhart in arranging the cranks 
so that the low-pressure led in forward motion, and the 
writer stated that the reason for the improvement in the 
steam distribution which was claimed was not apparent. 
The tables in Mr. Urquhart’s paper show that in the two 
engines which were compared—one with the low-pressure 
crank leading and the other with the high-pressure leading— 
one high-pressure cylinder was 18.5 inches in diameter 
while the other high-pressure cylinder was 18.11 inches in 
diameter, for the same notch in the quadrant the points of 
cut-off in the high-pressure cylinders were different, and 
in one engine the low-pressure cut-off was considerably 
later than the high-pressure, while in the other the distri- 
bution was very nearly the same in both cylinders. These 
points of difference are sufficient to vitiate the conclusions 
in regard to sequence of cranks. The only conclusion 


152 COMPOUND LOCOMOTIVES. 


which is apparent after a study of crank diagrams is that 
the sequence of cranks is of very little consequence. 

The following, from Engineering, referring to Mr. Urqu- 
hart’s tests, is worth noting : ‘‘ His experience is especially 
valuable as the steam pressure has not been increased in 
the converted engines, and thus there is no fear that it 
may be argued the economy claimed for the compounding 
has been partially, if not wholly, due to another cause, 
7. e., the higher pressure. This is a line of argument with 
which marine engineers were very familiar at one 
time. Mr. Urquhart’s experience is also valuable for 
another, and perhaps more, important reason. It is often 
claimed by those who do not believe in compounding loco- 
motives that the economy in fuel stated to be made is due 
more to the firing thantothesystem. . . . But Mr. Ur- 
quhart’s locomotives are mechanically stoked—that is, they 
are worked with liquid fuel—so that the ordinary condi- 
tions of good or bad firing do not apply. Whether the 
‘human factor’ crops up in other directions we do not 
know. . . . Theevidencein favor of the compound loco- 
motive, as being economical in fuel, is now of a very com- 
plete nature, and the ‘human factor’ argument is the 
chief one left to those who oppose the system.” 


Ob AE HE: (eT, 





AMERICAN PATENTS.—There are apparently but few 
United States patents which bear on the subject of com- 
pound locomotives, and most of these are of very recent 
date. The following list includes all which the writer has 
been able to find which appear to be of interest to designers 
of compound locomotives, although it is not improbable 
that others exist, carefully hidden by the erratic style of 
indexing adopted by the Patent Office. No attempt has 
been made to determine the breadth of the claims in any 


case. 

H. D. Dunbar, No. 264,937, Sept. 26, ed 276,368, April 24, 1883. Slide 
valves for tandem compound engine 

E. G. Davis, No. 274,571, March 27, #1883: "279, 544, June 19, 1883. Slide 
valve for tandem compound engines 

.B & J. A. Johnson, No. 351,921, Nov. 2,1886. Four-cylinder com- 
int at locomotive, with one receiver connected to all four- 
cylinders. 

T. W. Worsdell, No. 360,834, April 5, 1887. Compound engine with 
intercepting valve, substantially as previously described. 

A. von Borries, No 361,471, April 19, 1887. Compound locomotive 
with intercepting valve, substantially as previously described. 

R. Lindner, No. 4: 4,295, May 28, 1889. Starting gear for compound 
locomotives, substantially as previously described. 

R. H. Lapage, No. 405,569, June 18, 1889. Compound engine with 
intercepting and starting valve. 

R. H. Lapage, No. 405,570, June 18, 1889. Bogie compound locomo- 
tive with high pressure ‘cylinders on main frames and low-press- 
ure cylinders on a bogie truck, 

S. M. Vauclain, No. 406,011, June 25, 1889; 406,012, June 25, 1889. Four- 
cylinder compound locomotive with one or two piston steam-dis- 


tributing valves. 
A. J. Pitkin, No. “417, 083, Dec. 10, 1889. Two-cylinder compound 


locomotive with piston intercepting valve. 
F. W. Dean, No. 433,164, July 29, 1890. Compound engine. 


THE DUNBAR SysTEM.—A four-cylinder compound loco- 
motive was built by the Boston & Albany Railroad Com- 
pany in 1883, under the Dunbar patents. The cylinders 
were 12 inches and 20 inches in diameter, by 26 inches 
stroke, and were arranged tandem with the high-pressure 
and low-pressure pistons on the same piston rod. The en- 


154 COMPOUND LOCOMOTIVES. 


gine could be worked compound or non-compound at will. 
After working about seven months the locomotive was 
changed to asimple engine as it was apparently no more 
economical than the simple locomotives. Itis stated that 
the ports were too small and that the inventor was absent 
during the trial. As the locomotive was an experiment it 
is not surprising under the circumstances that the results 
were unsatisfactory. 

THE PITKIN TYPE ---A two-cylinder compound locomo- 


NN H le 
SN Bors N 
Ss Si SS => q 
- 





tive designed by Mr. A. J. Pitkin and built at the Schenec- 
tady Locomotive Works was put to work on the Michigan 
Central Railroad in September, 1889. The general arrange- 
ment of the cylinders and steam connections of this loco- 
motive is shown by Fig. 52. The distinctive feature of 
the engine is the intercepting valve, which is shown by Fig. 
53 which is a plan of the bushing which incloses the \ ive 
and by Fig. 54 which is a vertical section through the 
valve, bushing and saddle. 

The valve is shown in the position which it occupies in 


155 


COMPOUND LOCOMOTIVES, 


"7G ‘SL 


UU 









Sa ——— 1 VE ZZ 
HH 


WY, 











156 COMPOUND LOCOMOTIVES. 


starting; that is, before compound working begins. In this 
position the ports cand d are closed by the intercepting 
valve and the connection between the low-pressure steam 
chest and the receiver is thus cut off. The small port a 
(Fig. 58) is connected by a pipe and a pressure-reducing 
valve to the high-pressure. steam pipe. By this means 
steam at reduced pressure is admitted to the space b and 
thence, as indicated by the arrow, to the low-press- 
ure steam chest. As the parts of the valve on either 
side of bare of different diameters, the pressure in this 
space tends to hold the valve in the position shown in Fig. 
54, When the locomotive starts, the high-pressure cylin- 
der exhausts into the closed receiver, and the back pressure 
thus created acts upon the forward end of the inlercepting 
valve by means of the passage shown ate. The pressure 
in the receiver rapidly increases until the total pressure on 
the forward end of the valve is sufficient to overcome the 
total effective pressure at b, when the valve is forced to 
the back end of its stroke, the direct steam supply to the 
low-pressure cylinder is cut off and compound working be- 
gins. To prevent the valve moving too rapidly a dash-pot 
in the form of an oil cylinder, h,isadded. The valve stem 
is continued through this oil cylinder and is connected by 
levers to an index in the cab which indicates the position 
of the valve. 

The locomotive fitted with this intercepting valve has 
now been at work for several months with apparently 
satisfactory results. While its fuel saving capabilities have 
been demonstrated, it has not been thoroughly tested against 
a simple locomotive of proper dimensions to make a satis- 
factory comparison possible. The dimensions of this loco- 
motive are as follows: 


Diameter of h; p. cylinders. ss. snsccecteubescaboeeee 20 in, 
“ _LD. CaS eIPAT ct ee 29 in. 
Stroke of Pistons.) sc acc swke weve sine ceiciah tleliee cals seen 24 in. 
Ratio of cylinder volunies si. vest eaee cence ceien ae 2.1 
Size of steamt ports, HD. ss edeasrec bance eerie ae 18 in. X 14 in. 
ty Pe seme Ly Decks ces yeas ae enc ninmanea tee 20in. X 24in. 


COMPOUND LOCOMOTIVES. 157 


Size of exhaust ports. e WE ce ee ee wach ae 18in. x 3 in. 


MDC Beha ipa sistasie A atee eis Si oes 20in. X 3 in. 
Maximum travel of Males a ae 6% in. 
Lap of valve, h. Ps OULSIAG wate Pe ce pan ew tke cous 1 3gin. 
ANSI Cte hath see eee denne teas — 3in. 
Lap of valve, ue PD. OMtRIGO Sore. vas ces. Seas. . 14 in. 
cei ATSIO Oly eeretetn cmt Pete watete ies &cise “ts —1-16in. 
MUMIA OOLE soo fo 02 Os ss waisls viene das's vege secb anes dss 5-32 in. 
Peer OLIATIVING WHEEIE. ios oasis ces asncevcehacss 6 
inineter OL arivinge Wheels.2. 6.5. cceessscscdeecscet 68 in, 
EERO he soos, cca rehle > Geld atios oehe Gcscere cals Wagon top. 
Diameter of shell outside first ring.................. 58 in. 
Peieunose Of Pilates, steel: i. i662... tke ces ea ee ee- 9-16 and \% in. 
Size of firebox, inside................. length $6 3-16in.; width 42% in. 
Tubes, 247, 2 in.; length over tube sheets............ a Wit. 
Heating surface, pets Wa els Bal FESS nc . 1,540.3 sq. ft. 
HEGDORS we aceasta ies Bret tectalate alee she 187.1 sq. ft. 
ce * NASA aaidaciee Oe EN Gain ole ie ce aa Malet ial ute 1,677.4 sq. ft. 
GATATS BULTACO.. 002... cc etvcedemiersecscessccszecece 28.5 sq. ft. 
Total weight i INAWOPKINGE VOTO? os occ eiads.csce Ach scrnioe 126, 300 lbs. 
on driving wheels...........---«.. Paste 97, 000 Ibs. 
PEE WEE! DABS. ENDING. 6. oi css eds ever cess cence 29'ft. 6 in. 
Piet POOL DOGO isonet Gh cade 0) rte decwertvecese 12 ft. 2 in. 
EAL ECE 135 8 Sep ade lta ita ees onan nes sees 6 ft. 3in. 
Total wheel base, engine and tender......... sawn 48 ft. 


As built, the high-pressure valve had neither inside lap 
nor clearance ; the low-pressure valve had 4 inch inside 
lap, and the lead of both valves was 4; inch. These pro- 
portions have been changed to those given in the table of 
dimensions. In addition to this, the volume of the receiver 
has been increased from that of the high-pressure cylinder 
to 14 that volume, and the high-pressure clearance has been 
increased from 8} to 10 per cent. of the piston displacement, 
These changes were made after the indicator had demon- 
strated their necessity, and it will be seen they are entirely 
in accord with the proportions already recommended in 
these pages. Other locomotives of this type are now being 
constructed. 

THE VAUCLAIN TYPE.—A locomotive of this type was 
built by the Baldwin Locomotive Works in the fall of 1889, 
and was put to work on the Philadelphia Division of the 
Baltimore & Ohio Railroad. The general arrangement of 
the cylinders and valve isshown by Figs. 55 and 56. Re- 
ferring to Fig.55, h is the high-pressure cylinder, / is the 
low-pressure cylinder, and v is the valve bushing. The 


COMPOUND LOCOMOTIVES. 


158 


trans- 


s is 


method by which the power from both cylinder 


mitted through one cross-head is shown in Fig. 56, which 


ey 


Os 





So Sg ee 


Fig. 56, 
also shows the direct connections of the valve. 


The 
piston 


hollow 
illustrated by Fig. 


a 


is 
is 


distributing valve 
the action of which 


steam 
valve, 


COMPOUND LOCOMOTIVES. 159 


57, which represents a longitudinal section through the 
valve and the high-pressure cylinder.. Steam from the 
boiler enters the steam chest through the ports A, A, and 
passes thence by the port B, as indicated by arrows, to one 
end of the high-pressure cylinder. The exhaust from this 
cylinder passes through the valve to the port C, and thus 
to the low-pressure cylinder. The exhaust from the low- 
. pressure cylinder passes around the outside of the central 
portion of the valve, as indicated, to the exhaust pipe. 





Fig. 57. 


The method of distribution thus resembles that with the 
Dudgeon slide valve, which was at one time used for 
marine compound engines. 

The feature of this design which at first glance would 
seem to be most open to criticism is the connection to one 
cross-head of two pistons of which the centers are about 18 
inches apart and on which the total pressure must vary 
considerably. To determine the amount and variation of 
this difference of pressure with reasonable exactness an ex- 


160 COMPOUND LOCOMOTIVES. 


amination of a large number of indicator cards taken 
simultaneously from both high and low pressure cylinders. 
would be necessary. Some knowledge of the subject can, 
however, be gained from the examination of a few cards, 
and for this purpose the indicator diagrams shown in Fig. 
58 have been selected from a blue print sheet furnished by 
the builders of this locomotive. The data for these dia- 
grams are given as follows: 





Fig. 58. 
Card Rev. per Miles per Cut-off M. E. P. 
oO min hour p. cyl. h. p. cyl 
1 54 11 up 00 
2 218 44 Uy 5 
3 300 60 17/" 47 
4 150 30 9” 58 
Card MHP. M: EK. P; Horse Per cent. of 
No. 1. p. cyl. Lip: roth. i power. work byl. p. 
1 5 139 353.8 58 
2 27 75 836 54 
3 16 44 153.2 48 
4 24.5 68 607.2 54 


In making this comparison it has been assumed that the 
diagrams from the two ends of the cylinders are alike in 
each case. The diagrams were divided by ordinates as in. 


COMPOUND LOCOMOTIVES. 161 


Fig. 59, and the difference between the forward pressure 
on one side of each piston and the back pressure on the 
other side was plotted for each ordinate. A curve was thus 
established which represented the net effective pressure on 
each piston for various piston positions. Then the differ- 
ences of the ordinates of these two curves gave the curves 
shown in Fig. 59. The numbers of the curves in this 


Rs PO Seti bf 
H 


ee ene | 








Pal 
re 
ee 





aw eee oe we wpe es ee 


Fig. 59. 


diagram refer to the correspondingly numbered indicator 
- cards of Fig. 58, and the vertical distances above the base 
line A, A, represent the excess of the total pressure on the 
low-pressure piston above that on the high-pressure piston. 
Distances below the base line mean, of course, that thetotal 
_ pressure upon the high-pressure piston exceeds that on the 
low-pressure piston. The scale of pressures is about nine 
thousand pounds to one inch, and the stroke is taken to be 
in all cases from right to left. It will be seen that the 


162 COMPOUND LOCOMOTIVES. 


greatest difference in pressure is for the diagram taken at 
slow speed and late cut-off, and that for high speed and 
early cut-off the difference is comparatively small. Also 
that, according to curves 2 and 3, the effect of higher 
speed and lower initial pressure with the same cut-off is to 
greatly change the amount and distribution of the excess 
pressure. The scale to which Fig. 59 has been constructed 
is not sufficiently large to make the results entirely 
trustworthy, but the curves are sufficient to show that 
the variation in total pressures at ordinary run- 
ning speeds is approximately 5,000 pounds. The 
tendency is to tip the cross-head, and hence to bring 
an additional bending load on the piston rod of the under- 
loaded piston, which would apparently be most severe 
where this rod enters the cross-head. It does not follow 
that this fact is an argument against the adoption of this 
design, but simply that a varying load of, say, 5,000 
pounds acting with a leverage of about 18 inches, and hav- 
ing from 300 to 600 reversals per minute at ordinary speeds, 
_ is worth considering, and should be provided for in addi- 
tion to the usual stresses on piston rods. 

The principal dimensions of this locomotive are as fol- 
lows: 


Diameter’ of h:'p. cylinders... ...ctese sar wee ccc e ae stele eae 12 in. 
Diameter of ]. p. cylinders...........8...0 A heetaaenee ; 20:in: 
Stroke of pistons... 2.032% Sos sae bce cents rane Serene 24 in. 
Ratio of cylinder volumes *. <2... ce sence eee 5 2.78 
Number of driving wheels... c5...couceteur cocsnte css 4 
Diameter of ‘driving wheels... h.2.- ce. pases cess nen ener 66 in. 
Style of boileri ss. cis. wae us be weiik oy ton cng aie ree ee Wagon top. 
Diameter of Shell 34 5555s. Shin cesie cigs Oeics oe eel eaten suerte 58 in. 
Thickness. of shellsteel: <22i. cece ae e ees eee eee ¥% in. 
Sizolof flre:DOX fico tee ee oa scone length, 108 in.; width, 34 in. 
Tubes, 251, 2-1n., Jonethy; 6. cos. wc creme ominelecieetelc sietelers eteranets 11 ft. 10 in. 
Total weight in Working O©Ger sc... neces. cence tes these 105,000 lbs 
Total weight on driving wheels................ese0-++0% 75.000 Ibs, 
Total wheel base, engine. /2 2-4. sieace ce Len cle ctakitetesiet 21 ft. 10 in. 
Driving wheel bases .i* 0. bassinets cgndevercnctit i acatenee « eK 2B 


Total wheel base, engine and tender.. 


s eevee eceerseeeeeeees t. 


INDE: 


PAGE 

Acceleration of reciprocating parts.............eceeeeees ASGe 147 
AMErican COMpPOUN lOCOMOLIVES.......-ceccseccccccersecsce 153 
Baldwin four-cylinder compound........scccccscsesecccccces 157 
Clearance, effects of.......... Ah pn OE eer POLE EEEEE 23 
OHtDIneGr INC LCALON CATUS# 1: sine seni nes sonal: wd eva celsls cote hs ; 34 
Comparison of types..... ....--.. Pa teteene Se ccisi ae cscs eed aiaters 112, 143 
REE IeE RMA GEC tr erie er a ae Niod ct isc, aUlas’s wee eta! a04'eaesie dee 25 
POPU A ete ea ree esac a eae cheese mas oelnbee 26 

MICROTEL DANE 411 OVATE re rca bh ecle ss vos aes e's € bie eos co 77 
PrankvCiorts Gla eTranis Ole = hes eysie<cicscs skewed eine ve 67, 72, 103, 105 
Cranks, sequence of two-cylinder compound.............06. 79, 151 
TOUT GOR COM OUI et goc8 54s, cbei cc asbaccevesecs 124 

Se TLL Ol. O1LECL OL GHANPING veces nce sacs se cctas sleeve conae 18 
ratio, in four-cylinder compound...............0++. 118 

ev linCOrs: CONDEHSAULONIING Rot see werices.c cc eden ttaaasesiewe 77 
ratio of, three-cylinder compound............... 112 

4s two-cylinder compound..............e6- 22 

size of, tandem, four-cylinder compound........ 136 

- three-cylinder compound................. 95 

« e two-cylinder compound...............++. 58 

‘*  two-cylinder compound table............ 60 

Design of tandem COMMOUNG....... 5 sce ccc ccc scccceee Denise es 133 
SUMIMaar vO DLINC plOsnOLe saa cekice us dieaciwioccees valve 143 
Dimensions of four-cylinder compound, table............... 129 
TANG SMCOMPOUNG ess. ose 5 see -Caulsseic oases 140 
three-cylinder compound............cceeeeees 99, 101 

two-cylinder compound............... 38, 42, 62, 150, 156 

a UT CITI” WALT Cy MALOU lf. fchs eh codec oe ews ladle lolktots ce oe 52 
Drop in pressure between cylinders............ ER AA ae 16 
Dunbar four-cylinder COMPOUN .. 0... .deecccucesscsoe sone F 153 
HUCOMOMIV MP OL SULA LOL teaisisciacanaie Mca cb uistenlas chee eicie ee aie ae 148 
tandem, four-cylinder compound................. 142 
three-cylinder compound...........ccseecssee PEE: 111 
EVO-CYLNGO? COMPOUNG. fo cves sd ceevecsces cece 82 


“ 6s es th0I6; 2 3 dela TE Catala eee 83 


164 INDEX. 





PAGE 

Exhaust nozzlesis.0.. ov. isec ss de seu penal aeeeccneac sean 78 
Expansion, construction of curve of.... ..-1.%: -.-»sas eeawee 24 
total in two-cylinders........ oa eecakivenens wsletearene 15 

Formulas for division of work............. ‘vaere be 5 ehiale Se ea 116 
mean pressure.......... Seale ola .a Gs areve ghar sietiaeres mea a 

Four-cylinder compound, crank angles.........ceeeseeeeeees 124 
GIMEASIONS. Pees delees ce Snes n stak a siete cee 129, 162 

division’ of work, formula... ose nce cetera 116 

DUN DAR foc wsick wists \ seleittatt e one's ciate ener 153 

formulagsirs:. Fol vacd eetuare peas seta ce eee emewaire 115 

French, Pol. & MoR y vies dcsnssckn ven 119, 121, 123 
illustrations.:.... Mastek hee cauonyedsne ae 119, 121, 123, 158 

INGiCALOY GATGS: Se .Wiaise vases bes cle pase 138, 160 

Malleticsccct sccm ic ames se curb cise tree bie theater aan 127 

compound ratio Of GCUL-Ofl s/c. castes cease 118 

Tatiorol CVIINAGISs vem. k ess oe hee eats =e Ste 129 

reasons LOF USE Os se vue. eke eles $s /es gana 124 

sequence of cranks.......... eerie odulee tnd aie Re 124 

size of Cylind eres ci caks etecensedlens cs 35 0me 129, 136 

ae slide valves, proportions Of...........--seeeee 129 
LAY aw: steams distribution ii. ic. ccessc.5s cewek sce ame 116 
“Of. taridei oi. eee ara tears eren eo ae aie 130, 145 
Vauclain (Bald win)ficn ws seo sen eeeret oan 157 

of four-cylinder compound............ecseeece 119, 121, 123 
three-cylinder COMpOUNG.........cccesevrecs 97, 106 
Indicator cards, Baldwin four-cylinder...........sssceeeeeee 160 
COM DINE | ees Sis dibs ce dale see ee eee eae eene 34 

in, practice, tandem ss.\cc0%0...cek a ee) eee 131, 138 

two-cylinder. .. ..<0sssesaeueeee 27 

theoretical; tandem. js. . suck cisd oe eee 131 

+ three-cylinder........... aetna 90, 91 

Hy two cylinder......82.\s<8<ce ees 10 

Intercepting valves, Mallet........ teehantoaten PI ORIGHAR OL: : 50 
PipIn A geatt 35 ce ianiose eee amen aie cbiae eepaercente 155 

VONPESOLTIGS. pecan teem a ait ca a tetore erent ae 39 

WW Oradell vi tics sfceemeeteaminre ewiewew's ede’ (saa 43 

Lap of slide ‘valves: sis isscazuideesavssss choakeneeeroie tenets 57 
Lindner, startingvvalvens...c sco. cakes ch coe lacie cere 74 
type of two-cylinder compound...... ...sseecsecees 74 

Mallet distributing valve............ adic Ga eee els eters e SO Ten 52 
four-cylinder compounds... 0c ths cab ces tne neu eee 127 


intercepting -VAlVEs,.. sets scene twee ute ce ie etide mueeate 50 


i 


INDEX. 165 

PAGE 

PRPREGL LAL UIT VRLVGS Shas cdceciiscsukecces ceeceuccstsccwa esas 50 
EWU-CVLUING CL GOMIDOUNC san chao aeice celtics se iesieteaee d 36, 49 

Mean pressure, formulas.........ceseececees Hae a Se 12, 115 
P. L. & M. R’y. four-cylinder compounds .............. .-. 120 
AL Gen te ance ont cee ea EERO R aes ote anos hed weed aencees 153 
Piston speed... ......ces0.. Pete os is are Sica ten wh Ras Gases vere 146 
PULBMATY SIILOTOONGINIS VALVE, Creu aked phe hs kno 6ep ais'cle ts ae cide. cine 155 
UW O-CY UNO GE CONIDPOUNG 5 oa a docks occ cede vebeaiedwea ce ae 154 

Ports, size of steam.............. widen tes 1OEt Ra ce ere 56 
Pressure, drop in between cylinders.................eeee cee 16 
OduUlvalenbs 1 .ONG CY MNOS ys J.'6 s/s cokiclens ocacaecs 17 

final in low-pressure cylinder. .............es0.e0e- 15 

formulas for mean....... Tan es AOR cals cictie ob a 12, 115 
ATSMOCOLV CL rata tania Oates ecole cals miami a tle'elalsieieians ” <Sie JES RE: 

THORN GILCRLIVEbrhec, Socdagcas us svc teepea Nios etsek ss 17, 116 
THEOL ALM CH ibe Di ahiiet Maas eee © sisi ies Saisiacte sik’ s’o.0 che 14 

Ratio of cylinders, three-cylinder compound................ 112 
two-cylinder compound.....,........... 22 

HOLT ORV AMSIONE aicas eso eo seat cls's © Cars cibssieimieia'ce% s ciaccih 15 
Re-admission in low-pressure cylinder.............e...sse0e 21 
PCa VOT, CFOD IN. PIOMSUPG Ilse... .. ss ccdsccccunn Seccacncsesca 16 
WOVGSSUEO ie eER ECR eal iee son cba ces dee petuncediscaun 13, 33 

PV OLELIT) BD earv ede rOe fore heicicletecle <ie'vinis;areo:n aio ate ale'oia.e'bie ats 57, 157 
Reciprocating parts; acceleration Of......  ...cccessscsccece 147 
WELLS DIOR csiavie kere cscs ROYER cen crete 146 

MGA S O1rOr Us GiG GT Alih OL Judit ehive ce td os cas cwuccetchs ce dees 67, 72 
alae LOY SIZ Of. GYAINGELS sancicee occ ced vic Gerace) i delnelle eer 58 
NAMISHIATL LOSLAs sects ctus atieee animes peice Gbts citene cis oe nie eedeee 149 
Sequence of cranks in two-cylinder compound....... ete ate 
four-cylinder compound.............. 124 

Pe TR LVORs DTUDOFGOUS Ol cess acct tas sé uilecsccsensdaucendede 57 
PrArLING POWELL, COMPATISOH... iivsisae ds icdiees. eseesteesterns 144 
TIM OPINY 6 thane Souke Cap ceca ek ceete ch eves 75 

MISLIGU TIS oat ch a ck ewe us oon a th oles eve bk 69 

TANCE, TOUT-CYTNGOE so. focuses Vee a oe 137 

three-cylinder French type................ 107 

two-cylinder compound.......... Suet cetee 66 

WN OLD GOINOMIRULG Aba 32s s0cs s mativs oak a Gackes 109 

Worsdell-von Borries type.... ............ 70 

PAIN V OL Ve RANONEN. vic ia coeds iptassdeucsanrehvevesces 74 
WVEEIGOS sch crt ecanen eee c cavetietmew etude mae 50 

WOT ISOTTION (os waks ten ea vera tance aceawed ets 39 


166 INDEX. 
PAGE 
Steam distribution, tandem, four-cylinder.................. 132 
three-cylinder ......... se eeee ceeeeeeees 89 
Steam DASSARCS. 62755 Gy sami ssiee tans 540.48 bees Aneta Roo da occ 56 
Table, dimensions of two-cylinder compound.......... ---. 60, 62, 156 
French four-cylinder compound..... 129 
economy of two-cylinder compound...... .......... 83 
MEAN PPESSUTES jah cc divesdeece nds bes tie sels welt Genet 62 
slide valve *proportiONSs: cc... ose as noe a obese seni 57 
theoretical pressures Fic. cccics qoieisieie ciate eee ieee tere 14 
Tandem four-cylinder compound..............ccsescccessece 130, 145 
cylinders, size.0f-. oo.) cos dene’ cane ee omen nen 136 
CGOSIOT tii ciateletelelore's sha F ceeieine ste ons te Cone aes oe Eee 133 
CIMENSIONS 02 iiiei'o'ohle'eiere ons beewiecree cere © hem eLTaRette eaten 140 
ECONOMY. or Soh vc Eales o fall tea uleleinieln ete ante ers eee 142 
illustrations J22 6. ise atten ateaatic slow eeteeeteme ieee 138 
ANGICACOY'CATAS! 2. case enens seein bb shail olek s vied cis cata 131, 138 
Starting POWeLIsa wesc (core coe ae eine ee ects eee 137 
steam distribution : 5. pisces teeniene ces eset cece 132 
[At s 18) RS RR AA ei 5 pico cists oe apron eoaeticancmeen o- 130 
WIV 6. MOAT naan ie SL See See ee eects eee ss or 138, 141 
Theory of tandem four-cylinder compound................ 130 
three-cylinder COMPOUNG .............cccceccscecceee 89 
two-rcylinder, cOMpound... see veese ide oseenh ese 9 
Three-cylinder compound, crank angles ... ........... 90, 91, $4, 108 
diagrams of crank 6ffort.. \. cae ces ee enicioeeene 103, 105 
dimensions.......... sca rg gunie Wick ete he eee eee 99, 101 
distribution of workin, . 2.6.0.8... seamen 102 
OCONOLLY é Gepes's: «tie ais vig bis ose terete ache Oe ee 111 
Pen iinren 5 styicieian gas’ «oh i's saueiet eee 97, 106 
lustravionsii disc <s.0ctne ss (ss one eee 97, 100 
indicator cards, theoretical.................. 90, 91 
ratio of cylinders..;;; .)0/: pj. 40. «ce nee ee Pelee 112 
size of cylinders 6 ccc. ccs. ces oon nec 95 
Starting POWE?. i shisx c's a1 bee es roan eeee 107 
steam distribution ins: 2... «sues deca . 89 
WDD 5 eo cldsie dela vies s ceke coe teace tae 99, 103 
Tractive power, formulas. sc. o.00 Lae ie ececae ea ne anon atone 62 
Two-cylinder compound, Cost: ... ccc... coset ecessrt hess pene 85, 87 
dimensions fiq1 tite ssc oe eases eet 38, 42, 62, 150, 156 
Givision Of work in i. 234. va ics cgsicee oes coe 20 
ECONOMY: 5s, 5:0 crainccs 6 Seis on oheltletuels ee cent eee 82, 83 
indicator cards in practice.........csseee0 «ee 27 


theoretical........ wea Came 10 


PAGE 

Pere COE) 1 ANONOM UY THe. ow cw on iirc d'h's vale tine de aeisieca nese 74 

Malloy perigee ch ti wien oclewes cweistlels cele 36, 49 

PICRAIVEY Gia Seen ie Latha s whe FC as oohn o' 154 

THUGOT CYIINGOTE es os accke | Me-'de esa’ eee 22 

rules for »ize of cylinders...........-.. » aeteeis 58 

SOGUONCE Of CANE is eaves eek cec scene con 9 aA Gy 

size of cylinders........... abit ss tats ois 6 58, 60 

slide valves, proportions...:..........eee0--:: 57 

BUATGLD GUO Clie tees te ie oo ceerarks cs cds 66, 69, 70, 75 

valve gear adjustments.......5 sesccssees cee 44 

WOLUMEL POOEIV OL ss cc sas tee ile sak pidee’s cane alc 57 

WOM MOcriOs OY DOsrerc ts oho teaskss wkass dcae 37 

Worsdell BEM Nols titre (in's Ue tiistan share Semis aes 42 

RE CRA 2 2 oils e148 a cubits b dlipa 0's Cone ae dies aisesealas 149 

Valve gear, adjustments for two-cylinder compound...... 44 

IRL eee ia a wore iis rw iain vine ld Sp Galo evened ee ae 53, 55 

CADIG Of SLOAM) GIS6TIDULION aca cos occ cicesoesuneterese 46 

tandem, four-cylinder compound.................... 138, 141 

Valves, slide, proportions of................ Maes wide sepa Wad 57 

Vauclain four-cylinder compound....................ceceeee 157 

a alin@ Of TOCCLVOR ax chr tacos siete sen ei dicie tie a Sore coe Wewe son 57 

Von Borries intercepting Valve............5.005 ccccccsccccs 39 

FUIGO OL SIZE OL CY IINGOFSi arses cise csse-aenecke 58 

BUALELNS VOLVO Mee Mert cide ates - chats es Beck coe 39 

type of two-cylinder compound............... 37 

Webb type of three-cylinder compound.............cee0.0:- 99, 103 
Work, distribution in three-cylinder compound............ 102 

two-cylinder compound............. 20, 116 

Worsdell intercepting valve..... ....... ER ee ES es ae 43 

starting valve....... SoMBShEecr th: Wanitas et oe alors decors 43 

type of two-cylinder compound..... ............. 42 


“s BLATUNS DOWEL: ie dade Usbcussebebscacdoccess 70 


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Send for Descriptive 
Catalogues. 


Nathan Mfg. Co., 92 & 94 Liberty St., New York. 
ROGERS LOCOMOTIYE AND MACHINE WORKS, 


PATERSON, N. J. 
New York Office, 44 EXCHANGE PLACE, 


















































-—-MANUFACTURERS OF—— 


LOCOMOTIVE ENGINES AND TENDERS, 
AND OTHER RAILROAD MACHINERY. 


J. = ROGERS, President, 
UGHES, Secret: a PATERSON, N. J. 


RE BEN WELLS, Sup’t 


44 Exchange Place, New York. 


one VAS BR Cl erg 


NATIONAL cccottdrve BUILDER 


cacy | teal 


READ MORE BY GENERAL RAILROAD OFFICERS, MASTER 
MECHANICS AND MASTER CAR BUILDERS, THAN ANY 
OTHER PAPER PUBLISHED. DURING THE TWENTY-ONE 
YEARS OF ITS EXISTENCE THE PAPER HAS, STEADILY 
INCREASED IN VALUE, AND CONSEQUENTLY IN POPU- 
ZARLT Y. 

Aa Se we eee de 


The paper is edited by Mr. ANGUS SINCLAIR, a practical 
railroad engineer and mechanic, who was for many years engaged 
in the building, repairing, and operating of railroad machinery on 
British and American railways, and who is considered reliable 
authority on matters pertaining thereto. His book on Locomotive 
Engine Running and Management is in its seventeenth edition ; his 
book on Combustion in Locomotive Fire Boxes has met with an 
extraordinary demand, over twenty thousand copies having been 
sold in one year. 


EVERY ISSUE CONTAINS 
THOROUCHLY PRACTICAL ARTICLES 


ON TOPICS RELATING TO THE OPERATION OF RATLROADS AND TO THE 
DESIGN, CONSTRUCTION, REPAIR AND ECONOMICAL OPERATION OF 
ALL KINDS OF RAILROAD MACHINERY, WRITTEN BY MEN 
WHO CAN DO THE WORK THEY WRITE ABOUT. 

THE ARTICLES ARE 


NOTED FOR CLEARNESS AND SIMPLICITY 


OF DICTION, AND THEY ARE ALWAYS PRACTICAL. NO WRITING OVER 
THE HEADS OF ORDINARY BUSINESS MEN. 


muLoscription, = - -.62.00°%a year. 
Price, per copy, - - - 20 cents. 





National Car and Locomotive Builder, 
140 NASSAU STREET, NEW YORK. 


NATIONAL TUBE WORKS COMPANY 


OFFICES AND WAREHOUSES: 
70 FEDERAL STREET, BOSTON; 160 BRoADWAY, NEW YORK , 
CLINTON AND FULTON Sts., CHICAGO ; 988 NORTH SECOND ST., 
ST. LOUIS; SrxtH Avr. AND SMITHFIELD StT., PITTSBURG ; 
216 SouTH THIRD STREET, PHILADELPHIA, PA. 
—WORKS AT— 
McKEESPORT, PA., AND BOSTON, MASS. 
—MANUFACTURERS OF— 


Locomotive Boiler Tubes, 
STEAM, GAS AND WATER PIPE. 


PLAIN, ENAMELED, GALVANIZED AND 
KALAMEIN. 









etre 

















This Kalamein Prepara- 








me tion will resist the action of 


: Alkali Waters. 
































CLASS E. 


SPECIAL BRANDS OF TUBES, 
LOCOMOTIVE, KALAMEIN, SEMI-STEEL, FRANKLINITE, 


AND STANDARD 


DODGE 








Automatic 


uz1108 Oar 


Injector. 


ware NATIONAL. 


CONVERSE PATENT LOCK JOINT PIPE. 


Mack’s Lifting and Non-Lifting Locomotive Iniectors, 





—_—_— 


Boiler, in F 
Locomotive 





aie. 
&. a, 
bee 4S 
Smoke Stack BOX o 9 
$s % 
STEELS. 


\ 
| Quality Unsur- \ 


100 inches in width. 


SHOENBERGER & CO., 


‘PITTSBURGH. PA. 


Te 





Twist Drill and Machine Co. 


.. Morse 
ay 


SBS. 
















s <INEW BEDFORD, MASS.be 
SOLID, “MM, DRILLS FOR METAL 
SHELL, an 


Taper Reamers, With Straight 


MILLING CUTTERS, “SQN. or Taper 

Taps and Dies, Sockets, » 

DRILL GRINDING MACHINES, SN 
and Special Tools to Order. 





CUTS FOR THIS BOOK MADE BY 


GEO. H. BENEDICT & CO. 





THE LANE & BODLEY Co., 
CINCINNATI, ©., 


MANUFACTURE A STRICTLY FIRST-CLASS 





Corliss .*.,. Automatic .". Hingine. 


SATISFACTORILY IN USE IN FIRST-CLASS COMPANIES’ SHOPS. 


Shafting, Hangers, Pulleys, and Elevators. 


THE ONLY 


Successful Compound Locomotives 


ARE EQUIPPED WITH 


ALLEN-RICHARDSON BALANCED SLIDE-VALVES, 


Manufactured only by 


Estate of FW richardson, - - ‘Troy, N. Y. 


6000 STANDARD LOCOMOTIVES EQUIPPED 
WITH THESE VALVES. 





NATIONAL .ocetssv= BUILDER 


READ MORE BY GENERAL RAILROAD OFFICERS, MASTER MECHANICS AND MASTER CAR 
BUILDERS, THAN ANY OTHER PAPER PUBLISHED. DURING THE TWENTY-ONE 
YEARS OF ITS EXISTENCE THE PAPER HAS STEADILY INCREASED IN 
VALUE, AND CONSEQUENTLY IN POPULARITY. 

The paper is edited by Mr. ANGUS SINCLAIR, a practical railroad engineer and 
mechanic, who was for many years engaged in the building, repairing, and operating 
of railroad machinery on British and American railways, and who is considered 
rehable authority on matters pertaining thereto. His book on Locomotive Engine 
Running and Management is in its seventeenth edition; his book on Combustion in 
Locomotive Fire Boxes has met with an extraordinary demand, over twenty 
thousand copies having been sold in one year. 


—EVERY ISSUE CONTAINS— 
Thoroushliy FPractical Articles 


ON TOPICS RELATING TO THE OPERATION OF RAILROADS AND TO THE DESIGN, CON- 
STRUCTION, REPAIR AND ECONOMICAL OPERATION OF ALL KINDS OF RAILROAD 
MACHINERY, WRITTEN BY MEN WHO CAN DO THE WORK THEY WRITE 
ABOUT. THE ARTICLES ARE 


NOTED FOR CLEARNESS AND SIMPLICITY 


OF DICTION, AND THEY ARE ALWAYS PRACTICAL. NO WRITING OVER THE HEADS OF 
ORDINARY BUSINESS MEN. ij 


SUBSCRIPTION, - - - $2.00 A YEAR. 
PRICE, PER COPY, A tee 2 EN Los 
NATIONAL CAR AND LOCOMOTIVE BUILDER, 
140 Nassau Street, New York. 


BALDWIN LOCOMOTIVE WORKS, 


ESTABLISHED 1831. 


ANNUAL GAPACIT Yageeer 


























ompound * ** * 
*** x Locomotives 


And Locomotives adapted to every variety of service, 


and built accurately to standard gauges and templates. 
Like parts of different engines of same class perfectly 
interchangeable. Broad and Narrow Gauge Locomo- 
tives; Mine Locomotives by Steam or Compressed Air; 
Plantation Locomotives; Furnace Locomotives; Noise- 


less Motors for Street Railways, etc. 


BURNNAM, WILLIAMS & GO., 


PROPRIETORS, 


PHIiLA DEBI El Aw ee 


"NOILNEALLVY Ld INOUd AAICZORY TMM HALLaAT Ad SNOLLVOINOAWWOO 


e > 2-——_-_—__- 


“HSE aa uo ow Fav rr 
SISSuUAA JBOD JO SUL YUCIO UO Suisseiyg 10} syoer 






















































































































































































SYINNVH NVALS DNILOV LOWWIC Pue SyMaNVaXe 
TOL WLTTION ‘SAHONNd ‘SMOVE OITNVUCAH CTAOCVANT 


—HO BZHINALVd GNV HAY VW— 


“elles wl ae Be ES 9 xcs ey = + t ‘LEerrLs IND dated Soro vol ete a Gort ee ee 


‘NIOMmMDAGNAAd AUVHOIU 


Cast-Steel Works 


——OF— 


FRIED RAG 


ESSEN, GERMANY. 


American Office, 15 Gold St., New York. 


BuO. BOs eee 





REPRESENTED BY THOMAS PROSSER & SON. 





These Works cover an area of 1,200 acres, employ about 18,000 men, 
have the most improved plant, and stand unique, from the fact that 
they have their own Ore and Coal mines, Blast Furnaces, etc., and 
that every stage of manufacture is under their own supervision, and 
are not (like others) dependent on the open market for a miscellaneous 
assortment of crude material, which, in connection with 75 years’ 
experience, enables them to turn out a product of a very superior 
quality, second to none, and at the same time the different grades of 
Steel are always of the same uniform quality. 





Locomotive Tires, Steel-Tired Wheels, Axles, Crank Pins, 
Shafts and Steel Forgings up to 70 Tons. 





STEEL OF EVERY DESCRIPTION, FORGED, ROLLED, ETC., INTO 
ANY FORM OR ARTICLE DESIRED. 





Articles are furnished made of either Crucible or Open Hearth Steel, 
but for most purposes it is economy to use Crucible. 

Special attention is called to Krupp’s Crucible Steel Locomotive 
Tires, which for the past thirty-five years have proved themselves to 
be the best and cheapest in the market. 

When ordering locomotives or cars, it is economy to insert in the 
Specifications, that ‘‘ Krupp’s” Tires, Axles, Crank Pins, Piston, and 
Connecting Rods, Wheels, etc., are to be used, stating quality. 


“ 









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UNIVERSITY OF ILLINOIS-URBANA 


3 0112 073248244 





